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NAME

       perlapi - autogenerated documentation for the perl public API

DESCRIPTION

       This file contains the documentation of the perl public API generated by embed.pl,
       specifically a listing of functions, macros, flags, and variables that may be used by
       extension writers.  At the end is a list of functions which have yet to be documented.
       The interfaces of those are subject to change without notice.  Anything not listed here is
       not part of the public API, and should not be used by extension writers at all.  For these
       reasons, blindly using functions listed in proto.h is to be avoided when writing
       extensions.

       In Perl, unlike C, a string of characters may generally contain embedded "NUL" characters.
       Sometimes in the documentation a Perl string is referred to as a "buffer" to distinguish
       it from a C string, but sometimes they are both just referred to as strings.

       Note that all Perl API global variables must be referenced with the "PL_" prefix.  Again,
       those not listed here are not to be used by extension writers, and can be changed or
       removed without notice; same with macros.  Some macros are provided for compatibility with
       the older, unadorned names, but this support may be disabled in a future release.

       Perl was originally written to handle US-ASCII only (that is characters whose ordinal
       numbers are in the range 0 - 127).  And documentation and comments may still use the term
       ASCII, when sometimes in fact the entire range from 0 - 255 is meant.

       The non-ASCII characters below 256 can have various meanings, depending on various things.
       (See, most notably, perllocale.)  But usually the whole range can be referred to as
       ISO-8859-1.  Often, the term "Latin-1" (or "Latin1") is used as an equivalent for
       ISO-8859-1.  But some people treat "Latin1" as referring just to the characters in the
       range 128 through 255, or somethimes from 160 through 255.  This documentation uses
       "Latin1" and "Latin-1" to refer to all 256 characters.

       Note that Perl can be compiled and run under either ASCII or EBCDIC (See perlebcdic).
       Most of the documentation (and even comments in the code) ignore the EBCDIC possibility.
       For almost all purposes the differences are transparent.  As an example, under EBCDIC,
       instead of UTF-8, UTF-EBCDIC is used to encode Unicode strings, and so whenever this
       documentation refers to "utf8" (and variants of that name, including in function names),
       it also (essentially transparently) means "UTF-EBCDIC".  But the ordinals of characters
       differ between ASCII, EBCDIC, and the UTF- encodings, and a string encoded in UTF-EBCDIC
       may occupy a different number of bytes than in UTF-8.

       The listing below is alphabetical, case insensitive.

Array Manipulation Functions

       av_clear
               Frees the all the elements of an array, leaving it empty.  The XS equivalent of
               "@array = ()".  See also "av_undef".

               Note that it is possible that the actions of a destructor called directly or
               indirectly by freeing an element of the array could cause the reference count of
               the array itself to be reduced (e.g. by deleting an entry in the symbol table). So
               it is a possibility that the AV could have been freed (or even reallocated) on
               return from the call unless you hold a reference to it.

                       void    av_clear(AV *av)

       av_create_and_push
               NOTE: this function is experimental and may change or be removed without notice.

               Push an SV onto the end of the array, creating the array if necessary.  A small
               internal helper function to remove a commonly duplicated idiom.

                       void    av_create_and_push(AV **const avp,
                                                  SV *const val)

       av_create_and_unshift_one
               NOTE: this function is experimental and may change or be removed without notice.

               Unshifts an SV onto the beginning of the array, creating the array if necessary.
               A small internal helper function to remove a commonly duplicated idiom.

                       SV**    av_create_and_unshift_one(AV **const avp,
                                                         SV *const val)

       av_delete
               Deletes the element indexed by "key" from the array, makes the element mortal, and
               returns it.  If "flags" equals "G_DISCARD", the element is freed and NULL is
               returned. NULL is also returned if "key" is out of range.

               Perl equivalent: "splice(@myarray, $key, 1, undef)" (with the "splice" in void
               context if "G_DISCARD" is present).

                       SV*     av_delete(AV *av, SSize_t key, I32 flags)

       av_exists
               Returns true if the element indexed by "key" has been initialized.

               This relies on the fact that uninitialized array elements are set to "NULL".

               Perl equivalent: "exists($myarray[$key])".

                       bool    av_exists(AV *av, SSize_t key)

       av_extend
               Pre-extend an array.  The "key" is the index to which the array should be
               extended.

                       void    av_extend(AV *av, SSize_t key)

       av_fetch
               Returns the SV at the specified index in the array.  The "key" is the index.  If
               lval is true, you are guaranteed to get a real SV back (in case it wasn't real
               before), which you can then modify.  Check that the return value is non-null
               before dereferencing it to a "SV*".

               See "Understanding the Magic of Tied Hashes and Arrays" in perlguts for more
               information on how to use this function on tied arrays.

               The rough perl equivalent is $myarray[$key].

                       SV**    av_fetch(AV *av, SSize_t key, I32 lval)

       AvFILL  Same as "av_top_index()".  Deprecated, use "av_top_index()" instead.

                       int     AvFILL(AV* av)

       av_fill Set the highest index in the array to the given number, equivalent to Perl's
               "$#array = $fill;".

               The number of elements in the array will be "fill + 1" after "av_fill()" returns.
               If the array was previously shorter, then the additional elements appended are set
               to NULL.  If the array was longer, then the excess elements are freed.
               "av_fill(av, -1)" is the same as "av_clear(av)".

                       void    av_fill(AV *av, SSize_t fill)

       av_len  Same as "av_top_index".  Note that, unlike what the name implies, it returns the
               highest index in the array, so to get the size of the array you need to use
               "av_len(av) + 1".  This is unlike "sv_len", which returns what you would expect.

                       SSize_t av_len(AV *av)

       av_make Creates a new AV and populates it with a list of SVs.  The SVs are copied into the
               array, so they may be freed after the call to "av_make".  The new AV will have a
               reference count of 1.

               Perl equivalent: "my @new_array = ($scalar1, $scalar2, $scalar3...);"

                       AV*     av_make(SSize_t size, SV **strp)

       av_pop  Removes one SV from the end of the array, reducing its size by one and returning
               the SV (transferring control of one reference count) to the caller.  Returns
               &PL_sv_undef if the array is empty.

               Perl equivalent: "pop(@myarray);"

                       SV*     av_pop(AV *av)

       av_push Pushes an SV (transferring control of one reference count) onto the end of the
               array.  The array will grow automatically to accommodate the addition.

               Perl equivalent: "push @myarray, $val;".

                       void    av_push(AV *av, SV *val)

       av_shift
               Removes one SV from the start of the array, reducing its size by one and returning
               the SV (transferring control of one reference count) to the caller.  Returns
               &PL_sv_undef if the array is empty.

               Perl equivalent: "shift(@myarray);"

                       SV*     av_shift(AV *av)

       av_store
               Stores an SV in an array.  The array index is specified as "key".  The return
               value will be "NULL" if the operation failed or if the value did not need to be
               actually stored within the array (as in the case of tied arrays).  Otherwise, it
               can be dereferenced to get the "SV*" that was stored there (= "val")).

               Note that the caller is responsible for suitably incrementing the reference count
               of "val" before the call, and decrementing it if the function returned "NULL".

               Approximate Perl equivalent: "splice(@myarray, $key, 1, $val)".

               See "Understanding the Magic of Tied Hashes and Arrays" in perlguts for more
               information on how to use this function on tied arrays.

                       SV**    av_store(AV *av, SSize_t key, SV *val)

       av_tindex
               Same as "av_top_index()".

                       int     av_tindex(AV* av)

       av_top_index
               Returns the highest index in the array.  The number of elements in the array is
               "av_top_index(av) + 1".  Returns -1 if the array is empty.

               The Perl equivalent for this is $#myarray.

               (A slightly shorter form is "av_tindex".)

                       SSize_t av_top_index(AV *av)

       av_undef
               Undefines the array. The XS equivalent of "undef(@array)".

               As well as freeing all the elements of the array (like "av_clear()"), this also
               frees the memory used by the av to store its list of scalars.

               See "av_clear" for a note about the array possibly being invalid on return.

                       void    av_undef(AV *av)

       av_unshift
               Unshift the given number of "undef" values onto the beginning of the array.  The
               array will grow automatically to accommodate the addition.

               Perl equivalent: "unshift @myarray, ((undef) x $num);"

                       void    av_unshift(AV *av, SSize_t num)

       get_av  Returns the AV of the specified Perl global or package array with the given name
               (so it won't work on lexical variables).  "flags" are passed to "gv_fetchpv".  If
               "GV_ADD" is set and the Perl variable does not exist then it will be created.  If
               "flags" is zero and the variable does not exist then NULL is returned.

               Perl equivalent: "@{"$name"}".

               NOTE: the perl_ form of this function is deprecated.

                       AV*     get_av(const char *name, I32 flags)

       newAV   Creates a new AV.  The reference count is set to 1.

               Perl equivalent: "my @array;".

                       AV*     newAV()

       sortsv  In-place sort an array of SV pointers with the given comparison routine.

               Currently this always uses mergesort.  See "sortsv_flags" for a more flexible
               routine.

                       void    sortsv(SV** array, size_t num_elts,
                                      SVCOMPARE_t cmp)

       sortsv_flags
               In-place sort an array of SV pointers with the given comparison routine, with
               various SORTf_* flag options.

                       void    sortsv_flags(SV** array, size_t num_elts,
                                            SVCOMPARE_t cmp, U32 flags)

Callback Functions

       call_argv
               Performs a callback to the specified named and package-scoped Perl subroutine with
               "argv" (a "NULL"-terminated array of strings) as arguments.  See perlcall.

               Approximate Perl equivalent: "&{"$sub_name"}(@$argv)".

               NOTE: the perl_ form of this function is deprecated.

                       I32     call_argv(const char* sub_name, I32 flags,
                                         char** argv)

       call_method
               Performs a callback to the specified Perl method.  The blessed object must be on
               the stack.  See perlcall.

               NOTE: the perl_ form of this function is deprecated.

                       I32     call_method(const char* methname, I32 flags)

       call_pv Performs a callback to the specified Perl sub.  See perlcall.

               NOTE: the perl_ form of this function is deprecated.

                       I32     call_pv(const char* sub_name, I32 flags)

       call_sv Performs a callback to the Perl sub specified by the SV.

               If neither the "G_METHOD" nor "G_METHOD_NAMED" flag is supplied, the SV may be any
               of a CV, a GV, a reference to a CV, a reference to a GV or "SvPV(sv)" will be used
               as the name of the sub to call.

               If the "G_METHOD" flag is supplied, the SV may be a reference to a CV or
               "SvPV(sv)" will be used as the name of the method to call.

               If the "G_METHOD_NAMED" flag is supplied, "SvPV(sv)" will be used as the name of
               the method to call.

               Some other values are treated specially for internal use and should not be
               depended on.

               See perlcall.

               NOTE: the perl_ form of this function is deprecated.

                       I32     call_sv(SV* sv, VOL I32 flags)

       ENTER   Opening bracket on a callback.  See "LEAVE" and perlcall.

                               ENTER;

       ENTER_with_name(name)
               Same as "ENTER", but when debugging is enabled it also associates the given
               literal string with the new scope.

                               ENTER_with_name(name);

       eval_pv Tells Perl to "eval" the given string in scalar context and return an SV* result.

               NOTE: the perl_ form of this function is deprecated.

                       SV*     eval_pv(const char* p, I32 croak_on_error)

       eval_sv Tells Perl to "eval" the string in the SV.  It supports the same flags as
               "call_sv", with the obvious exception of "G_EVAL".  See perlcall.

               NOTE: the perl_ form of this function is deprecated.

                       I32     eval_sv(SV* sv, I32 flags)

       FREETMPS
               Closing bracket for temporaries on a callback.  See "SAVETMPS" and perlcall.

                               FREETMPS;

       LEAVE   Closing bracket on a callback.  See "ENTER" and perlcall.

                               LEAVE;

       LEAVE_with_name(name)
               Same as "LEAVE", but when debugging is enabled it first checks that the scope has
               the given name. "name" must be a "NUL"-terminated literal string.

                               LEAVE_with_name(name);

       SAVETMPS
               Opening bracket for temporaries on a callback.  See "FREETMPS" and perlcall.

                               SAVETMPS;

Character case changing

       Perl uses "full" Unicode case mappings.  This means that converting a single character to
       another case may result in a sequence of more than one character.  For example, the
       uppercase of "ß" (LATIN SMALL LETTER SHARP S) is the two character sequence "SS".  This
       presents some complications   The lowercase of all characters in the range 0..255 is a
       single character, and thus "toLOWER_L1" is furnished.  But, "toUPPER_L1" can't exist, as
       it couldn't return a valid result for all legal inputs.  Instead "toUPPER_uvchr" has an
       API that does allow every possible legal result to be returned.)  Likewise no other
       function that is crippled by not being able to give the correct results for the full range
       of possible inputs has been implemented here.

       toFOLD  Converts the specified character to foldcase.  If the input is anything but an
               ASCII uppercase character, that input character itself is returned.  Variant
               "toFOLD_A" is equivalent.  (There is no equivalent "to_FOLD_L1" for the full
               Latin1 range, as the full generality of "toFOLD_uvchr" is needed there.)

                       U8      toFOLD(U8 ch)

       toFOLD_utf8
               This is like "toFOLD_utf8_safe", but doesn't have the "e" parameter  The function
               therefore can't check if it is reading beyond the end of the string.  Starting in
               Perl v5.30, it will take the "e" parameter, becoming a synonym for
               "toFOLD_utf8_safe".  At that time every program that uses it will have to be
               changed to successfully compile.  In the meantime, the first runtime call to
               "toFOLD_utf8" from each call point in the program will raise a deprecation
               warning, enabled by default.  You can convert your program now to use
               "toFOLD_utf8_safe", and avoid the warnings, and get an extra measure of
               protection, or you can wait until v5.30, when you'll be forced to add the "e"
               parameter.

                       UV      toFOLD_utf8(U8* p, U8* s, STRLEN* lenp)

       toFOLD_utf8_safe
               Converts the first UTF-8 encoded character in the sequence starting at "p" and
               extending no further than "e - 1" to its foldcase version, and stores that in
               UTF-8 in "s", and its length in bytes in "lenp".  Note that the buffer pointed to
               by "s" needs to be at least "UTF8_MAXBYTES_CASE+1" bytes since the foldcase
               version may be longer than the original character.

               The first code point of the foldcased version is returned (but note, as explained
               at the top of this section, that there may be more).

               The suffix "_safe" in the function's name indicates that it will not attempt to
               read beyond "e - 1", provided that the constraint "s < e" is true (this is
               asserted for in "-DDEBUGGING" builds).  If the UTF-8 for the input character is
               malformed in some way, the program may croak, or the function may return the
               REPLACEMENT CHARACTER, at the discretion of the implementation, and subject to
               change in future releases.

                       UV      toFOLD_utf8_safe(U8* p, U8* e, U8* s,
                                                STRLEN* lenp)

       toFOLD_uvchr
               Converts the code point "cp" to its foldcase version, and stores that in UTF-8 in
               "s", and its length in bytes in "lenp".  The code point is interpreted as native
               if less than 256; otherwise as Unicode.  Note that the buffer pointed to by "s"
               needs to be at least "UTF8_MAXBYTES_CASE+1" bytes since the foldcase version may
               be longer than the original character.

               The first code point of the foldcased version is returned (but note, as explained
               at the top of this section, that there may be more).

                       UV      toFOLD_uvchr(UV cp, U8* s, STRLEN* lenp)

       toLOWER Converts the specified character to lowercase.  If the input is anything but an
               ASCII uppercase character, that input character itself is returned.  Variant
               "toLOWER_A" is equivalent.

                       U8      toLOWER(U8 ch)

       toLOWER_L1
               Converts the specified Latin1 character to lowercase.  The results are undefined
               if the input doesn't fit in a byte.

                       U8      toLOWER_L1(U8 ch)

       toLOWER_LC
               Converts the specified character to lowercase using the current locale's rules, if
               possible; otherwise returns the input character itself.

                       U8      toLOWER_LC(U8 ch)

       toLOWER_utf8
               This is like "toLOWER_utf8_safe", but doesn't have the "e" parameter  The function
               therefore can't check if it is reading beyond the end of the string.  Starting in
               Perl v5.30, it will take the "e" parameter, becoming a synonym for
               "toLOWER_utf8_safe".  At that time every program that uses it will have to be
               changed to successfully compile.  In the meantime, the first runtime call to
               "toLOWER_utf8" from each call point in the program will raise a deprecation
               warning, enabled by default.  You can convert your program now to use
               "toLOWER_utf8_safe", and avoid the warnings, and get an extra measure of
               protection, or you can wait until v5.30, when you'll be forced to add the "e"
               parameter.

                       UV      toLOWER_utf8(U8* p, U8* s, STRLEN* lenp)

       toLOWER_utf8_safe
               Converts the first UTF-8 encoded character in the sequence starting at "p" and
               extending no further than "e - 1" to its lowercase version, and stores that in
               UTF-8 in "s", and its length in bytes in "lenp".  Note that the buffer pointed to
               by "s" needs to be at least "UTF8_MAXBYTES_CASE+1" bytes since the lowercase
               version may be longer than the original character.

               The first code point of the lowercased version is returned (but note, as explained
               at the top of this section, that there may be more).

               The suffix "_safe" in the function's name indicates that it will not attempt to
               read beyond "e - 1", provided that the constraint "s < e" is true (this is
               asserted for in "-DDEBUGGING" builds).  If the UTF-8 for the input character is
               malformed in some way, the program may croak, or the function may return the
               REPLACEMENT CHARACTER, at the discretion of the implementation, and subject to
               change in future releases.

                       UV      toLOWER_utf8_safe(U8* p, U8* e, U8* s,
                                                 STRLEN* lenp)

       toLOWER_uvchr
               Converts the code point "cp" to its lowercase version, and stores that in UTF-8 in
               "s", and its length in bytes in "lenp".  The code point is interpreted as native
               if less than 256; otherwise as Unicode.  Note that the buffer pointed to by "s"
               needs to be at least "UTF8_MAXBYTES_CASE+1" bytes since the lowercase version may
               be longer than the original character.

               The first code point of the lowercased version is returned (but note, as explained
               at the top of this section, that there may be more).

                       UV      toLOWER_uvchr(UV cp, U8* s, STRLEN* lenp)

       toTITLE Converts the specified character to titlecase.  If the input is anything but an
               ASCII lowercase character, that input character itself is returned.  Variant
               "toTITLE_A" is equivalent.  (There is no "toTITLE_L1" for the full Latin1 range,
               as the full generality of "toTITLE_uvchr" is needed there.  Titlecase is not a
               concept used in locale handling, so there is no functionality for that.)

                       U8      toTITLE(U8 ch)

       toTITLE_utf8
               This is like "toLOWER_utf8_safe", but doesn't have the "e" parameter  The function
               therefore can't check if it is reading beyond the end of the string.  Starting in
               Perl v5.30, it will take the "e" parameter, becoming a synonym for
               "toTITLE_utf8_safe".  At that time every program that uses it will have to be
               changed to successfully compile.  In the meantime, the first runtime call to
               "toTITLE_utf8" from each call point in the program will raise a deprecation
               warning, enabled by default.  You can convert your program now to use
               "toTITLE_utf8_safe", and avoid the warnings, and get an extra measure of
               protection, or you can wait until v5.30, when you'll be forced to add the "e"
               parameter.

                       UV      toTITLE_utf8(U8* p, U8* s, STRLEN* lenp)

       toTITLE_utf8_safe
               Converts the first UTF-8 encoded character in the sequence starting at "p" and
               extending no further than "e - 1" to its titlecase version, and stores that in
               UTF-8 in "s", and its length in bytes in "lenp".  Note that the buffer pointed to
               by "s" needs to be at least "UTF8_MAXBYTES_CASE+1" bytes since the titlecase
               version may be longer than the original character.

               The first code point of the titlecased version is returned (but note, as explained
               at the top of this section, that there may be more).

               The suffix "_safe" in the function's name indicates that it will not attempt to
               read beyond "e - 1", provided that the constraint "s < e" is true (this is
               asserted for in "-DDEBUGGING" builds).  If the UTF-8 for the input character is
               malformed in some way, the program may croak, or the function may return the
               REPLACEMENT CHARACTER, at the discretion of the implementation, and subject to
               change in future releases.

                       UV      toTITLE_utf8_safe(U8* p, U8* e, U8* s,
                                                 STRLEN* lenp)

       toTITLE_uvchr
               Converts the code point "cp" to its titlecase version, and stores that in UTF-8 in
               "s", and its length in bytes in "lenp".  The code point is interpreted as native
               if less than 256; otherwise as Unicode.  Note that the buffer pointed to by "s"
               needs to be at least "UTF8_MAXBYTES_CASE+1" bytes since the titlecase version may
               be longer than the original character.

               The first code point of the titlecased version is returned (but note, as explained
               at the top of this section, that there may be more).

                       UV      toTITLE_uvchr(UV cp, U8* s, STRLEN* lenp)

       toUPPER Converts the specified character to uppercase.  If the input is anything but an
               ASCII lowercase character, that input character itself is returned.  Variant
               "toUPPER_A" is equivalent.

                       U8      toUPPER(U8 ch)

       toUPPER_utf8
               This is like "toUPPER_utf8_safe", but doesn't have the "e" parameter  The function
               therefore can't check if it is reading beyond the end of the string.  Starting in
               Perl v5.30, it will take the "e" parameter, becoming a synonym for
               "toUPPER_utf8_safe".  At that time every program that uses it will have to be
               changed to successfully compile.  In the meantime, the first runtime call to
               "toUPPER_utf8" from each call point in the program will raise a deprecation
               warning, enabled by default.  You can convert your program now to use
               "toUPPER_utf8_safe", and avoid the warnings, and get an extra measure of
               protection, or you can wait until v5.30, when you'll be forced to add the "e"
               parameter.

                       UV      toUPPER_utf8(U8* p, U8* s, STRLEN* lenp)

       toUPPER_utf8_safe
               Converts the first UTF-8 encoded character in the sequence starting at "p" and
               extending no further than "e - 1" to its uppercase version, and stores that in
               UTF-8 in "s", and its length in bytes in "lenp".  Note that the buffer pointed to
               by "s" needs to be at least "UTF8_MAXBYTES_CASE+1" bytes since the uppercase
               version may be longer than the original character.

               The first code point of the uppercased version is returned (but note, as explained
               at the top of this section, that there may be more).

               The suffix "_safe" in the function's name indicates that it will not attempt to
               read beyond "e - 1", provided that the constraint "s < e" is true (this is
               asserted for in "-DDEBUGGING" builds).  If the UTF-8 for the input character is
               malformed in some way, the program may croak, or the function may return the
               REPLACEMENT CHARACTER, at the discretion of the implementation, and subject to
               change in future releases.

                       UV      toUPPER_utf8_safe(U8* p, U8* e, U8* s,
                                                 STRLEN* lenp)

       toUPPER_uvchr
               Converts the code point "cp" to its uppercase version, and stores that in UTF-8 in
               "s", and its length in bytes in "lenp".  The code point is interpreted as native
               if less than 256; otherwise as Unicode.  Note that the buffer pointed to by "s"
               needs to be at least "UTF8_MAXBYTES_CASE+1" bytes since the uppercase version may
               be longer than the original character.

               The first code point of the uppercased version is returned (but note, as explained
               at the top of this section, that there may be more.)

                       UV      toUPPER_uvchr(UV cp, U8* s, STRLEN* lenp)

Character classification

       This section is about functions (really macros) that classify characters into types, such
       as punctuation versus alphabetic, etc.  Most of these are analogous to regular expression
       character classes.  (See "POSIX Character Classes" in perlrecharclass.)  There are several
       variants for each class.  (Not all macros have all variants; each item below lists the
       ones valid for it.)  None are affected by "use bytes", and only the ones with "LC" in the
       name are affected by the current locale.

       The base function, e.g., "isALPHA()", takes an octet (either a "char" or a "U8") as input
       and returns a boolean as to whether or not the character represented by that octet is (or
       on non-ASCII platforms, corresponds to) an ASCII character in the named class based on
       platform, Unicode, and Perl rules.  If the input is a number that doesn't fit in an octet,
       FALSE is returned.

       Variant "isFOO_A" (e.g., "isALPHA_A()") is identical to the base function with no suffix
       "_A".  This variant is used to emphasize by its name that only ASCII-range characters can
       return TRUE.

       Variant "isFOO_L1" imposes the Latin-1 (or EBCDIC equivalent) character set onto the
       platform.  That is, the code points that are ASCII are unaffected, since ASCII is a subset
       of Latin-1.  But the non-ASCII code points are treated as if they are Latin-1 characters.
       For example, "isWORDCHAR_L1()" will return true when called with the code point 0xDF,
       which is a word character in both ASCII and EBCDIC (though it represents different
       characters in each).

       Variant "isFOO_uvchr" is like the "isFOO_L1" variant, but accepts any UV code point as
       input.  If the code point is larger than 255, Unicode rules are used to determine if it is
       in the character class.  For example, "isWORDCHAR_uvchr(0x100)" returns TRUE, since 0x100
       is LATIN CAPITAL LETTER A WITH MACRON in Unicode, and is a word character.

       Variant "isFOO_utf8_safe" is like "isFOO_uvchr", but is used for UTF-8 encoded strings.
       Each call classifies one character, even if the string contains many.  This variant takes
       two parameters.  The first, "p", is a pointer to the first byte of the character to be
       classified.  (Recall that it may take more than one byte to represent a character in UTF-8
       strings.)  The second parameter, "e", points to anywhere in the string beyond the first
       character, up to one byte past the end of the entire string.  The suffix "_safe" in the
       function's name indicates that it will not attempt to read beyond "e - 1", provided that
       the constraint "s < e" is true (this is asserted for in "-DDEBUGGING" builds).  If the
       UTF-8 for the input character is malformed in some way, the program may croak, or the
       function may return FALSE, at the discretion of the implementation, and subject to change
       in future releases.

       Variant "isFOO_utf8" is like "isFOO_utf8_safe", but takes just a single parameter, "p",
       which has the same meaning as the corresponding parameter does in "isFOO_utf8_safe".  The
       function therefore can't check if it is reading beyond the end of the string.  Starting in
       Perl v5.30, it will take a second parameter, becoming a synonym for "isFOO_utf8_safe".  At
       that time every program that uses it will have to be changed to successfully compile.  In
       the meantime, the first runtime call to "isFOO_utf8" from each call point in the program
       will raise a deprecation warning, enabled by default.  You can convert your program now to
       use "isFOO_utf8_safe", and avoid the warnings, and get an extra measure of protection, or
       you can wait until v5.30, when you'll be forced to add the "e" parameter.

       Variant "isFOO_LC" is like the "isFOO_A" and "isFOO_L1" variants, but the result is based
       on the current locale, which is what "LC" in the name stands for.  If Perl can determine
       that the current locale is a UTF-8 locale, it uses the published Unicode rules; otherwise,
       it uses the C library function that gives the named classification.  For example,
       "isDIGIT_LC()" when not in a UTF-8 locale returns the result of calling "isdigit()".
       FALSE is always returned if the input won't fit into an octet.  On some platforms where
       the C library function is known to be defective, Perl changes its result to follow the
       POSIX standard's rules.

       Variant "isFOO_LC_uvchr" is like "isFOO_LC", but is defined on any UV.  It returns the
       same as "isFOO_LC" for input code points less than 256, and returns the hard-coded, not-
       affected-by-locale, Unicode results for larger ones.

       Variant "isFOO_LC_utf8_safe" is like "isFOO_LC_uvchr", but is used for UTF-8 encoded
       strings.  Each call classifies one character, even if the string contains many.  This
       variant takes two parameters.  The first, "p", is a pointer to the first byte of the
       character to be classified.  (Recall that it may take more than one byte to represent a
       character in UTF-8 strings.) The second parameter, "e", points to anywhere in the string
       beyond the first character, up to one byte past the end of the entire string.  The suffix
       "_safe" in the function's name indicates that it will not attempt to read beyond "e - 1",
       provided that the constraint "s < e" is true (this is asserted for in "-DDEBUGGING"
       builds).  If the UTF-8 for the input character is malformed in some way, the program may
       croak, or the function may return FALSE, at the discretion of the implementation, and
       subject to change in future releases.

       Variant "isFOO_LC_utf8" is like "isFOO_LC_utf8_safe", but takes just a single parameter,
       "p", which has the same meaning as the corresponding parameter does in
       "isFOO_LC_utf8_safe".  The function therefore can't check if it is reading beyond the end
       of the string.  Starting in Perl v5.30, it will take a second parameter, becoming a
       synonym for "isFOO_LC_utf8_safe".  At that time every program that uses it will have to be
       changed to successfully compile.  In the meantime, the first runtime call to
       "isFOO_LC_utf8" from each call point in the program will raise a deprecation warning,
       enabled by default.  You can convert your program now to use "isFOO_LC_utf8_safe", and
       avoid the warnings, and get an extra measure of protection, or you can wait until v5.30,
       when you'll be forced to add the "e" parameter.

       isALPHA Returns a boolean indicating whether the specified character is an alphabetic
               character, analogous to "m/[[:alpha:]]/".  See the top of this section for an
               explanation of variants "isALPHA_A", "isALPHA_L1", "isALPHA_uvchr",
               "isALPHA_utf8_safe", "isALPHA_LC", "isALPHA_LC_uvchr", and "isALPHA_LC_utf8_safe".

                       bool    isALPHA(char ch)

       isALPHANUMERIC
               Returns a boolean indicating whether the specified character is a either an
               alphabetic character or decimal digit, analogous to "m/[[:alnum:]]/".  See the top
               of this section for an explanation of variants "isALPHANUMERIC_A",
               "isALPHANUMERIC_L1", "isALPHANUMERIC_uvchr", "isALPHANUMERIC_utf8_safe",
               "isALPHANUMERIC_LC", "isALPHANUMERIC_LC_uvchr", and "isALPHANUMERIC_LC_utf8_safe".

                       bool    isALPHANUMERIC(char ch)

       isASCII Returns a boolean indicating whether the specified character is one of the 128
               characters in the ASCII character set, analogous to "m/[[:ascii:]]/".  On non-
               ASCII platforms, it returns TRUE iff this character corresponds to an ASCII
               character.  Variants "isASCII_A()" and "isASCII_L1()" are identical to
               "isASCII()".  See the top of this section for an explanation of variants
               "isASCII_uvchr", "isASCII_utf8_safe", "isASCII_LC", "isASCII_LC_uvchr", and
               "isASCII_LC_utf8_safe".  Note, however, that some platforms do not have the C
               library routine "isascii()".  In these cases, the variants whose names contain
               "LC" are the same as the corresponding ones without.

               Also note, that because all ASCII characters are UTF-8 invariant (meaning they
               have the exact same representation (always a single byte) whether encoded in UTF-8
               or not), "isASCII" will give the correct results when called with any byte in any
               string encoded or not in UTF-8.  And similarly "isASCII_utf8_safe" will work
               properly on any string encoded or not in UTF-8.

                       bool    isASCII(char ch)

       isBLANK Returns a boolean indicating whether the specified character is a character
               considered to be a blank, analogous to "m/[[:blank:]]/".  See the top of this
               section for an explanation of variants "isBLANK_A", "isBLANK_L1", "isBLANK_uvchr",
               "isBLANK_utf8_safe", "isBLANK_LC", "isBLANK_LC_uvchr", and "isBLANK_LC_utf8_safe".
               Note, however, that some platforms do not have the C library routine "isblank()".
               In these cases, the variants whose names contain "LC" are the same as the
               corresponding ones without.

                       bool    isBLANK(char ch)

       isCNTRL Returns a boolean indicating whether the specified character is a control
               character, analogous to "m/[[:cntrl:]]/".  See the top of this section for an
               explanation of variants "isCNTRL_A", "isCNTRL_L1", "isCNTRL_uvchr",
               "isCNTRL_utf8_safe", "isCNTRL_LC", "isCNTRL_LC_uvchr", and "isCNTRL_LC_utf8_safe"
               On EBCDIC platforms, you almost always want to use the "isCNTRL_L1" variant.

                       bool    isCNTRL(char ch)

       isDIGIT Returns a boolean indicating whether the specified character is a digit, analogous
               to "m/[[:digit:]]/".  Variants "isDIGIT_A" and "isDIGIT_L1" are identical to
               "isDIGIT".  See the top of this section for an explanation of variants
               "isDIGIT_uvchr", "isDIGIT_utf8_safe", "isDIGIT_LC", "isDIGIT_LC_uvchr", and
               "isDIGIT_LC_utf8_safe".

                       bool    isDIGIT(char ch)

       isGRAPH Returns a boolean indicating whether the specified character is a graphic
               character, analogous to "m/[[:graph:]]/".  See the top of this section for an
               explanation of variants "isGRAPH_A", "isGRAPH_L1", "isGRAPH_uvchr",
               "isGRAPH_utf8_safe", "isGRAPH_LC", "isGRAPH_LC_uvchr", and "isGRAPH_LC_utf8_safe".

                       bool    isGRAPH(char ch)

       isIDCONT
               Returns a boolean indicating whether the specified character can be the second or
               succeeding character of an identifier.  This is very close to, but not quite the
               same as the official Unicode property "XID_Continue".  The difference is that this
               returns true only if the input character also matches "isWORDCHAR".  See the top
               of this section for an explanation of variants "isIDCONT_A", "isIDCONT_L1",
               "isIDCONT_uvchr", "isIDCONT_utf8_safe", "isIDCONT_LC", "isIDCONT_LC_uvchr", and
               "isIDCONT_LC_utf8_safe".

                       bool    isIDCONT(char ch)

       isIDFIRST
               Returns a boolean indicating whether the specified character can be the first
               character of an identifier.  This is very close to, but not quite the same as the
               official Unicode property "XID_Start".  The difference is that this returns true
               only if the input character also matches "isWORDCHAR".  See the top of this
               section for an explanation of variants "isIDFIRST_A", "isIDFIRST_L1",
               "isIDFIRST_uvchr", "isIDFIRST_utf8_safe", "isIDFIRST_LC", "isIDFIRST_LC_uvchr",
               and "isIDFIRST_LC_utf8_safe".

                       bool    isIDFIRST(char ch)

       isLOWER Returns a boolean indicating whether the specified character is a lowercase
               character, analogous to "m/[[:lower:]]/".  See the top of this section for an
               explanation of variants "isLOWER_A", "isLOWER_L1", "isLOWER_uvchr",
               "isLOWER_utf8_safe", "isLOWER_LC", "isLOWER_LC_uvchr", and "isLOWER_LC_utf8_safe".

                       bool    isLOWER(char ch)

       isOCTAL Returns a boolean indicating whether the specified character is an octal digit,
               [0-7].  The only two variants are "isOCTAL_A" and "isOCTAL_L1"; each is identical
               to "isOCTAL".

                       bool    isOCTAL(char ch)

       isPRINT Returns a boolean indicating whether the specified character is a printable
               character, analogous to "m/[[:print:]]/".  See the top of this section for an
               explanation of variants "isPRINT_A", "isPRINT_L1", "isPRINT_uvchr",
               "isPRINT_utf8_safe", "isPRINT_LC", "isPRINT_LC_uvchr", and "isPRINT_LC_utf8_safe".

                       bool    isPRINT(char ch)

       isPSXSPC
               (short for Posix Space) Starting in 5.18, this is identical in all its forms to
               the corresponding "isSPACE()" macros.  The locale forms of this macro are
               identical to their corresponding "isSPACE()" forms in all Perl releases.  In
               releases prior to 5.18, the non-locale forms differ from their "isSPACE()" forms
               only in that the "isSPACE()" forms don't match a Vertical Tab, and the
               "isPSXSPC()" forms do.  Otherwise they are identical.  Thus this macro is
               analogous to what "m/[[:space:]]/" matches in a regular expression.  See the top
               of this section for an explanation of variants "isPSXSPC_A", "isPSXSPC_L1",
               "isPSXSPC_uvchr", "isPSXSPC_utf8_safe", "isPSXSPC_LC", "isPSXSPC_LC_uvchr", and
               "isPSXSPC_LC_utf8_safe".

                       bool    isPSXSPC(char ch)

       isPUNCT Returns a boolean indicating whether the specified character is a punctuation
               character, analogous to "m/[[:punct:]]/".  Note that the definition of what is
               punctuation isn't as straightforward as one might desire.  See "POSIX Character
               Classes" in perlrecharclass for details.  See the top of this section for an
               explanation of variants "isPUNCT_A", "isPUNCT_L1", "isPUNCT_uvchr",
               "isPUNCT_utf8_safe", "isPUNCT_LC", "isPUNCT_LC_uvchr", and "isPUNCT_LC_utf8_safe".

                       bool    isPUNCT(char ch)

       isSPACE Returns a boolean indicating whether the specified character is a whitespace
               character.  This is analogous to what "m/\s/" matches in a regular expression.
               Starting in Perl 5.18 this also matches what "m/[[:space:]]/" does.  Prior to
               5.18, only the locale forms of this macro (the ones with "LC" in their names)
               matched precisely what "m/[[:space:]]/" does.  In those releases, the only
               difference, in the non-locale variants, was that "isSPACE()" did not match a
               vertical tab.  (See "isPSXSPC" for a macro that matches a vertical tab in all
               releases.)  See the top of this section for an explanation of variants
               "isSPACE_A", "isSPACE_L1", "isSPACE_uvchr", "isSPACE_utf8_safe", "isSPACE_LC",
               "isSPACE_LC_uvchr", and "isSPACE_LC_utf8_safe".

                       bool    isSPACE(char ch)

       isUPPER Returns a boolean indicating whether the specified character is an uppercase
               character, analogous to "m/[[:upper:]]/".  See the top of this section for an
               explanation of variants "isUPPER_A", "isUPPER_L1", "isUPPER_uvchr",
               "isUPPER_utf8_safe", "isUPPER_LC", "isUPPER_LC_uvchr", and "isUPPER_LC_utf8_safe".

                       bool    isUPPER(char ch)

       isWORDCHAR
               Returns a boolean indicating whether the specified character is a character that
               is a word character, analogous to what "m/\w/" and "m/[[:word:]]/" match in a
               regular expression.  A word character is an alphabetic character, a decimal digit,
               a connecting punctuation character (such as an underscore), or a "mark" character
               that attaches to one of those (like some sort of accent).  "isALNUM()" is a
               synonym provided for backward compatibility, even though a word character includes
               more than the standard C language meaning of alphanumeric.  See the top of this
               section for an explanation of variants "isWORDCHAR_A", "isWORDCHAR_L1",
               "isWORDCHAR_uvchr", and "isWORDCHAR_utf8_safe".  "isWORDCHAR_LC",
               "isWORDCHAR_LC_uvchr", and "isWORDCHAR_LC_utf8_safe" are also as described there,
               but additionally include the platform's native underscore.

                       bool    isWORDCHAR(char ch)

       isXDIGIT
               Returns a boolean indicating whether the specified character is a hexadecimal
               digit.  In the ASCII range these are "[0-9A-Fa-f]".  Variants "isXDIGIT_A()" and
               "isXDIGIT_L1()" are identical to "isXDIGIT()".  See the top of this section for an
               explanation of variants "isXDIGIT_uvchr", "isXDIGIT_utf8_safe", "isXDIGIT_LC",
               "isXDIGIT_LC_uvchr", and "isXDIGIT_LC_utf8_safe".

                       bool    isXDIGIT(char ch)

Cloning an interpreter

       perl_clone
               Create and return a new interpreter by cloning the current one.

               "perl_clone" takes these flags as parameters:

               "CLONEf_COPY_STACKS" - is used to, well, copy the stacks also, without it we only
               clone the data and zero the stacks, with it we copy the stacks and the new perl
               interpreter is ready to run at the exact same point as the previous one.  The
               pseudo-fork code uses "COPY_STACKS" while the threads->create doesn't.

               "CLONEf_KEEP_PTR_TABLE" - "perl_clone" keeps a ptr_table with the pointer of the
               old variable as a key and the new variable as a value, this allows it to check if
               something has been cloned and not clone it again but rather just use the value and
               increase the refcount.  If "KEEP_PTR_TABLE" is not set then "perl_clone" will kill
               the ptr_table using the function "ptr_table_free(PL_ptr_table); PL_ptr_table =
               NULL;", reason to keep it around is if you want to dup some of your own variable
               who are outside the graph perl scans, an example of this code is in threads.xs
               create.

               "CLONEf_CLONE_HOST" - This is a win32 thing, it is ignored on unix, it tells perls
               win32host code (which is c++) to clone itself, this is needed on win32 if you want
               to run two threads at the same time, if you just want to do some stuff in a
               separate perl interpreter and then throw it away and return to the original one,
               you don't need to do anything.

                       PerlInterpreter* perl_clone(
                                            PerlInterpreter *proto_perl,
                                            UV flags
                                        )

Compile-time scope hooks

       BhkDISABLE
               NOTE: this function is experimental and may change or be removed without notice.

               Temporarily disable an entry in this BHK structure, by clearing the appropriate
               flag.  "which" is a preprocessor token indicating which entry to disable.

                       void    BhkDISABLE(BHK *hk, which)

       BhkENABLE
               NOTE: this function is experimental and may change or be removed without notice.

               Re-enable an entry in this BHK structure, by setting the appropriate flag.
               "which" is a preprocessor token indicating which entry to enable.  This will
               assert (under -DDEBUGGING) if the entry doesn't contain a valid pointer.

                       void    BhkENABLE(BHK *hk, which)

       BhkENTRY_set
               NOTE: this function is experimental and may change or be removed without notice.

               Set an entry in the BHK structure, and set the flags to indicate it is valid.
               "which" is a preprocessing token indicating which entry to set.  The type of "ptr"
               depends on the entry.

                       void    BhkENTRY_set(BHK *hk, which, void *ptr)

       blockhook_register
               NOTE: this function is experimental and may change or be removed without notice.

               Register a set of hooks to be called when the Perl lexical scope changes at
               compile time.  See "Compile-time scope hooks" in perlguts.

               NOTE: this function must be explicitly called as Perl_blockhook_register with an
               aTHX_ parameter.

                       void    Perl_blockhook_register(pTHX_ BHK *hk)

COP Hint Hashes

       cophh_2hv
               NOTE: this function is experimental and may change or be removed without notice.

               Generates and returns a standard Perl hash representing the full set of key/value
               pairs in the cop hints hash "cophh".  "flags" is currently unused and must be
               zero.

                       HV *    cophh_2hv(const COPHH *cophh, U32 flags)

       cophh_copy
               NOTE: this function is experimental and may change or be removed without notice.

               Make and return a complete copy of the cop hints hash "cophh".

                       COPHH * cophh_copy(COPHH *cophh)

       cophh_delete_pv
               NOTE: this function is experimental and may change or be removed without notice.

               Like "cophh_delete_pvn", but takes a nul-terminated string instead of a
               string/length pair.

                       COPHH * cophh_delete_pv(const COPHH *cophh,
                                               const char *key, U32 hash,
                                               U32 flags)

       cophh_delete_pvn
               NOTE: this function is experimental and may change or be removed without notice.

               Delete a key and its associated value from the cop hints hash "cophh", and returns
               the modified hash.  The returned hash pointer is in general not the same as the
               hash pointer that was passed in.  The input hash is consumed by the function, and
               the pointer to it must not be subsequently used.  Use "cophh_copy" if you need
               both hashes.

               The key is specified by "keypv" and "keylen".  If "flags" has the "COPHH_KEY_UTF8"
               bit set, the key octets are interpreted as UTF-8, otherwise they are interpreted
               as Latin-1.  "hash" is a precomputed hash of the key string, or zero if it has not
               been precomputed.

                       COPHH * cophh_delete_pvn(COPHH *cophh,
                                                const char *keypv,
                                                STRLEN keylen, U32 hash,
                                                U32 flags)

       cophh_delete_pvs
               NOTE: this function is experimental and may change or be removed without notice.

               Like "cophh_delete_pvn", but takes a "NUL"-terminated literal string instead of a
               string/length pair, and no precomputed hash.

                       COPHH * cophh_delete_pvs(const COPHH *cophh,
                                                const char *key, U32 flags)

       cophh_delete_sv
               NOTE: this function is experimental and may change or be removed without notice.

               Like "cophh_delete_pvn", but takes a Perl scalar instead of a string/length pair.

                       COPHH * cophh_delete_sv(const COPHH *cophh, SV *key,
                                               U32 hash, U32 flags)

       cophh_fetch_pv
               NOTE: this function is experimental and may change or be removed without notice.

               Like "cophh_fetch_pvn", but takes a nul-terminated string instead of a
               string/length pair.

                       SV *    cophh_fetch_pv(const COPHH *cophh,
                                              const char *key, U32 hash,
                                              U32 flags)

       cophh_fetch_pvn
               NOTE: this function is experimental and may change or be removed without notice.

               Look up the entry in the cop hints hash "cophh" with the key specified by "keypv"
               and "keylen".  If "flags" has the "COPHH_KEY_UTF8" bit set, the key octets are
               interpreted as UTF-8, otherwise they are interpreted as Latin-1.  "hash" is a
               precomputed hash of the key string, or zero if it has not been precomputed.
               Returns a mortal scalar copy of the value associated with the key, or
               &PL_sv_placeholder if there is no value associated with the key.

                       SV *    cophh_fetch_pvn(const COPHH *cophh,
                                               const char *keypv,
                                               STRLEN keylen, U32 hash,
                                               U32 flags)

       cophh_fetch_pvs
               NOTE: this function is experimental and may change or be removed without notice.

               Like "cophh_fetch_pvn", but takes a "NUL"-terminated literal string instead of a
               string/length pair, and no precomputed hash.

                       SV *    cophh_fetch_pvs(const COPHH *cophh,
                                               const char *key, U32 flags)

       cophh_fetch_sv
               NOTE: this function is experimental and may change or be removed without notice.

               Like "cophh_fetch_pvn", but takes a Perl scalar instead of a string/length pair.

                       SV *    cophh_fetch_sv(const COPHH *cophh, SV *key,
                                              U32 hash, U32 flags)

       cophh_free
               NOTE: this function is experimental and may change or be removed without notice.

               Discard the cop hints hash "cophh", freeing all resources associated with it.

                       void    cophh_free(COPHH *cophh)

       cophh_new_empty
               NOTE: this function is experimental and may change or be removed without notice.

               Generate and return a fresh cop hints hash containing no entries.

                       COPHH * cophh_new_empty()

       cophh_store_pv
               NOTE: this function is experimental and may change or be removed without notice.

               Like "cophh_store_pvn", but takes a nul-terminated string instead of a
               string/length pair.

                       COPHH * cophh_store_pv(const COPHH *cophh,
                                              const char *key, U32 hash,
                                              SV *value, U32 flags)

       cophh_store_pvn
               NOTE: this function is experimental and may change or be removed without notice.

               Stores a value, associated with a key, in the cop hints hash "cophh", and returns
               the modified hash.  The returned hash pointer is in general not the same as the
               hash pointer that was passed in.  The input hash is consumed by the function, and
               the pointer to it must not be subsequently used.  Use "cophh_copy" if you need
               both hashes.

               The key is specified by "keypv" and "keylen".  If "flags" has the "COPHH_KEY_UTF8"
               bit set, the key octets are interpreted as UTF-8, otherwise they are interpreted
               as Latin-1.  "hash" is a precomputed hash of the key string, or zero if it has not
               been precomputed.

               "value" is the scalar value to store for this key.  "value" is copied by this
               function, which thus does not take ownership of any reference to it, and later
               changes to the scalar will not be reflected in the value visible in the cop hints
               hash.  Complex types of scalar will not be stored with referential integrity, but
               will be coerced to strings.

                       COPHH * cophh_store_pvn(COPHH *cophh, const char *keypv,
                                               STRLEN keylen, U32 hash,
                                               SV *value, U32 flags)

       cophh_store_pvs
               NOTE: this function is experimental and may change or be removed without notice.

               Like "cophh_store_pvn", but takes a "NUL"-terminated literal string instead of a
               string/length pair, and no precomputed hash.

                       COPHH * cophh_store_pvs(const COPHH *cophh,
                                               const char *key, SV *value,
                                               U32 flags)

       cophh_store_sv
               NOTE: this function is experimental and may change or be removed without notice.

               Like "cophh_store_pvn", but takes a Perl scalar instead of a string/length pair.

                       COPHH * cophh_store_sv(const COPHH *cophh, SV *key,
                                              U32 hash, SV *value, U32 flags)

COP Hint Reading

       cop_hints_2hv
               Generates and returns a standard Perl hash representing the full set of hint
               entries in the cop "cop".  "flags" is currently unused and must be zero.

                       HV *    cop_hints_2hv(const COP *cop, U32 flags)

       cop_hints_fetch_pv
               Like "cop_hints_fetch_pvn", but takes a nul-terminated string instead of a
               string/length pair.

                       SV *    cop_hints_fetch_pv(const COP *cop,
                                                  const char *key, U32 hash,
                                                  U32 flags)

       cop_hints_fetch_pvn
               Look up the hint entry in the cop "cop" with the key specified by "keypv" and
               "keylen".  If "flags" has the "COPHH_KEY_UTF8" bit set, the key octets are
               interpreted as UTF-8, otherwise they are interpreted as Latin-1.  "hash" is a
               precomputed hash of the key string, or zero if it has not been precomputed.
               Returns a mortal scalar copy of the value associated with the key, or
               &PL_sv_placeholder if there is no value associated with the key.

                       SV *    cop_hints_fetch_pvn(const COP *cop,
                                                   const char *keypv,
                                                   STRLEN keylen, U32 hash,
                                                   U32 flags)

       cop_hints_fetch_pvs
               Like "cop_hints_fetch_pvn", but takes a "NUL"-terminated literal string instead of
               a string/length pair, and no precomputed hash.

                       SV *    cop_hints_fetch_pvs(const COP *cop,
                                                   const char *key, U32 flags)

       cop_hints_fetch_sv
               Like "cop_hints_fetch_pvn", but takes a Perl scalar instead of a string/length
               pair.

                       SV *    cop_hints_fetch_sv(const COP *cop, SV *key,
                                                  U32 hash, U32 flags)

Custom Operators

       custom_op_register
               Register a custom op.  See "Custom Operators" in perlguts.

               NOTE: this function must be explicitly called as Perl_custom_op_register with an
               aTHX_ parameter.

                       void    Perl_custom_op_register(pTHX_
                                                       Perl_ppaddr_t ppaddr,
                                                       const XOP *xop)

       custom_op_xop
               Return the XOP structure for a given custom op.  This macro should be considered
               internal to "OP_NAME" and the other access macros: use them instead.  This macro
               does call a function.  Prior to 5.19.6, this was implemented as a function.

               NOTE: this function must be explicitly called as Perl_custom_op_xop with an aTHX_
               parameter.

                       const XOP * Perl_custom_op_xop(pTHX_ const OP *o)

       XopDISABLE
               Temporarily disable a member of the XOP, by clearing the appropriate flag.

                       void    XopDISABLE(XOP *xop, which)

       XopENABLE
               Reenable a member of the XOP which has been disabled.

                       void    XopENABLE(XOP *xop, which)

       XopENTRY
               Return a member of the XOP structure.  "which" is a cpp token indicating which
               entry to return.  If the member is not set this will return a default value.  The
               return type depends on "which".  This macro evaluates its arguments more than
               once.  If you are using "Perl_custom_op_xop" to retreive a "XOP *" from a "OP *",
               use the more efficient "XopENTRYCUSTOM" instead.

                               XopENTRY(XOP *xop, which)

       XopENTRYCUSTOM
               Exactly like "XopENTRY(XopENTRY(Perl_custom_op_xop(aTHX_ o), which)" but more
               efficient.  The "which" parameter is identical to "XopENTRY".

                               XopENTRYCUSTOM(const OP *o, which)

       XopENTRY_set
               Set a member of the XOP structure.  "which" is a cpp token indicating which entry
               to set.  See "Custom Operators" in perlguts for details about the available
               members and how they are used.  This macro evaluates its argument more than once.

                       void    XopENTRY_set(XOP *xop, which, value)

       XopFLAGS
               Return the XOP's flags.

                       U32     XopFLAGS(XOP *xop)

CV Manipulation Functions

       This section documents functions to manipulate CVs which are code-values, or subroutines.
       For more information, see perlguts.

       caller_cx
               The XSUB-writer's equivalent of caller().  The returned "PERL_CONTEXT" structure
               can be interrogated to find all the information returned to Perl by "caller".
               Note that XSUBs don't get a stack frame, so "caller_cx(0, NULL)" will return
               information for the immediately-surrounding Perl code.

               This function skips over the automatic calls to &DB::sub made on the behalf of the
               debugger.  If the stack frame requested was a sub called by "DB::sub", the return
               value will be the frame for the call to "DB::sub", since that has the correct line
               number/etc. for the call site.  If dbcxp is non-"NULL", it will be set to a
               pointer to the frame for the sub call itself.

                       const PERL_CONTEXT * caller_cx(
                                                I32 level,
                                                const PERL_CONTEXT **dbcxp
                                            )

       CvSTASH Returns the stash of the CV.  A stash is the symbol table hash, containing the
               package-scoped variables in the package where the subroutine was defined.  For
               more information, see perlguts.

               This also has a special use with XS AUTOLOAD subs.  See "Autoloading with XSUBs"
               in perlguts.

                       HV*     CvSTASH(CV* cv)

       find_runcv
               Locate the CV corresponding to the currently executing sub or eval.  If "db_seqp"
               is non_null, skip CVs that are in the DB package and populate *db_seqp with the
               cop sequence number at the point that the DB:: code was entered.  (This allows
               debuggers to eval in the scope of the breakpoint rather than in the scope of the
               debugger itself.)

                       CV*     find_runcv(U32 *db_seqp)

       get_cv  Uses "strlen" to get the length of "name", then calls "get_cvn_flags".

               NOTE: the perl_ form of this function is deprecated.

                       CV*     get_cv(const char* name, I32 flags)

       get_cvn_flags
               Returns the CV of the specified Perl subroutine.  "flags" are passed to
               "gv_fetchpvn_flags".  If "GV_ADD" is set and the Perl subroutine does not exist
               then it will be declared (which has the same effect as saying "sub name;").  If
               "GV_ADD" is not set and the subroutine does not exist then NULL is returned.

               NOTE: the perl_ form of this function is deprecated.

                       CV*     get_cvn_flags(const char* name, STRLEN len,
                                             I32 flags)

"xsubpp" variables and internal functions

       ax      Variable which is setup by "xsubpp" to indicate the stack base offset, used by the
               "ST", "XSprePUSH" and "XSRETURN" macros.  The "dMARK" macro must be called prior
               to setup the "MARK" variable.

                       I32     ax

       CLASS   Variable which is setup by "xsubpp" to indicate the class name for a C++ XS
               constructor.  This is always a "char*".  See "THIS".

                       char*   CLASS

       dAX     Sets up the "ax" variable.  This is usually handled automatically by "xsubpp" by
               calling "dXSARGS".

                               dAX;

       dAXMARK Sets up the "ax" variable and stack marker variable "mark".  This is usually
               handled automatically by "xsubpp" by calling "dXSARGS".

                               dAXMARK;

       dITEMS  Sets up the "items" variable.  This is usually handled automatically by "xsubpp"
               by calling "dXSARGS".

                               dITEMS;

       dUNDERBAR
               Sets up any variable needed by the "UNDERBAR" macro.  It used to define
               "padoff_du", but it is currently a noop.  However, it is strongly advised to still
               use it for ensuring past and future compatibility.

                               dUNDERBAR;

       dXSARGS Sets up stack and mark pointers for an XSUB, calling "dSP" and "dMARK".  Sets up
               the "ax" and "items" variables by calling "dAX" and "dITEMS".  This is usually
               handled automatically by "xsubpp".

                               dXSARGS;

       dXSI32  Sets up the "ix" variable for an XSUB which has aliases.  This is usually handled
               automatically by "xsubpp".

                               dXSI32;

       items   Variable which is setup by "xsubpp" to indicate the number of items on the stack.
               See "Variable-length Parameter Lists" in perlxs.

                       I32     items

       ix      Variable which is setup by "xsubpp" to indicate which of an XSUB's aliases was
               used to invoke it.  See "The ALIAS: Keyword" in perlxs.

                       I32     ix

       RETVAL  Variable which is setup by "xsubpp" to hold the return value for an XSUB.  This is
               always the proper type for the XSUB.  See "The RETVAL Variable" in perlxs.

                       (whatever)      RETVAL

       ST      Used to access elements on the XSUB's stack.

                       SV*     ST(int ix)

       THIS    Variable which is setup by "xsubpp" to designate the object in a C++ XSUB.  This
               is always the proper type for the C++ object.  See "CLASS" and "Using XS With C++"
               in perlxs.

                       (whatever)      THIS

       UNDERBAR
               The SV* corresponding to the $_ variable.  Works even if there is a lexical $_ in
               scope.

       XS      Macro to declare an XSUB and its C parameter list.  This is handled by "xsubpp".
               It is the same as using the more explicit "XS_EXTERNAL" macro.

       XS_EXTERNAL
               Macro to declare an XSUB and its C parameter list explicitly exporting the
               symbols.

       XS_INTERNAL
               Macro to declare an XSUB and its C parameter list without exporting the symbols.
               This is handled by "xsubpp" and generally preferable over exporting the XSUB
               symbols unnecessarily.

Debugging Utilities

       dump_all
               Dumps the entire optree of the current program starting at "PL_main_root" to
               "STDERR".  Also dumps the optrees for all visible subroutines in "PL_defstash".

                       void    dump_all()

       dump_packsubs
               Dumps the optrees for all visible subroutines in "stash".

                       void    dump_packsubs(const HV* stash)

       op_class
               Given an op, determine what type of struct it has been allocated as.  Returns one
               of the OPclass enums, such as OPclass_LISTOP.

                       OPclass op_class(const OP *o)

       op_dump Dumps the optree starting at OP "o" to "STDERR".

                       void    op_dump(const OP *o)

       sv_dump Dumps the contents of an SV to the "STDERR" filehandle.

               For an example of its output, see Devel::Peek.

                       void    sv_dump(SV* sv)

Display and Dump functions

       pv_display
               Similar to

                 pv_escape(dsv,pv,cur,pvlim,PERL_PV_ESCAPE_QUOTE);

               except that an additional "\0" will be appended to the string when len > cur and
               pv[cur] is "\0".

               Note that the final string may be up to 7 chars longer than pvlim.

                       char*   pv_display(SV *dsv, const char *pv, STRLEN cur,
                                          STRLEN len, STRLEN pvlim)

       pv_escape
               Escapes at most the first "count" chars of "pv" and puts the results into "dsv"
               such that the size of the escaped string will not exceed "max" chars and will not
               contain any incomplete escape sequences.  The number of bytes escaped will be
               returned in the "STRLEN *escaped" parameter if it is not null.  When the "dsv"
               parameter is null no escaping actually occurs, but the number of bytes that would
               be escaped were it not null will be calculated.

               If flags contains "PERL_PV_ESCAPE_QUOTE" then any double quotes in the string will
               also be escaped.

               Normally the SV will be cleared before the escaped string is prepared, but when
               "PERL_PV_ESCAPE_NOCLEAR" is set this will not occur.

               If "PERL_PV_ESCAPE_UNI" is set then the input string is treated as UTF-8 if
               "PERL_PV_ESCAPE_UNI_DETECT" is set then the input string is scanned using
               "is_utf8_string()" to determine if it is UTF-8.

               If "PERL_PV_ESCAPE_ALL" is set then all input chars will be output using "\x01F1"
               style escapes, otherwise if "PERL_PV_ESCAPE_NONASCII" is set, only non-ASCII chars
               will be escaped using this style; otherwise, only chars above 255 will be so
               escaped; other non printable chars will use octal or common escaped patterns like
               "\n".  Otherwise, if "PERL_PV_ESCAPE_NOBACKSLASH" then all chars below 255 will be
               treated as printable and will be output as literals.

               If "PERL_PV_ESCAPE_FIRSTCHAR" is set then only the first char of the string will
               be escaped, regardless of max.  If the output is to be in hex, then it will be
               returned as a plain hex sequence.  Thus the output will either be a single char,
               an octal escape sequence, a special escape like "\n" or a hex value.

               If "PERL_PV_ESCAPE_RE" is set then the escape char used will be a "%" and not a
               "\\".  This is because regexes very often contain backslashed sequences, whereas
               "%" is not a particularly common character in patterns.

               Returns a pointer to the escaped text as held by "dsv".

                       char*   pv_escape(SV *dsv, char const * const str,
                                         const STRLEN count, const STRLEN max,
                                         STRLEN * const escaped,
                                         const U32 flags)

       pv_pretty
               Converts a string into something presentable, handling escaping via "pv_escape()"
               and supporting quoting and ellipses.

               If the "PERL_PV_PRETTY_QUOTE" flag is set then the result will be double quoted
               with any double quotes in the string escaped.  Otherwise if the
               "PERL_PV_PRETTY_LTGT" flag is set then the result be wrapped in angle brackets.

               If the "PERL_PV_PRETTY_ELLIPSES" flag is set and not all characters in string were
               output then an ellipsis "..." will be appended to the string.  Note that this
               happens AFTER it has been quoted.

               If "start_color" is non-null then it will be inserted after the opening quote (if
               there is one) but before the escaped text.  If "end_color" is non-null then it
               will be inserted after the escaped text but before any quotes or ellipses.

               Returns a pointer to the prettified text as held by "dsv".

                       char*   pv_pretty(SV *dsv, char const * const str,
                                         const STRLEN count, const STRLEN max,
                                         char const * const start_color,
                                         char const * const end_color,
                                         const U32 flags)

Embedding Functions

       cv_clone
               Clone a CV, making a lexical closure.  "proto" supplies the prototype of the
               function: its code, pad structure, and other attributes.  The prototype is
               combined with a capture of outer lexicals to which the code refers, which are
               taken from the currently-executing instance of the immediately surrounding code.

                       CV *    cv_clone(CV *proto)

       cv_name Returns an SV containing the name of the CV, mainly for use in error reporting.
               The CV may actually be a GV instead, in which case the returned SV holds the GV's
               name.  Anything other than a GV or CV is treated as a string already holding the
               sub name, but this could change in the future.

               An SV may be passed as a second argument.  If so, the name will be assigned to it
               and it will be returned.  Otherwise the returned SV will be a new mortal.

               If "flags" has the "CV_NAME_NOTQUAL" bit set, then the package name will not be
               included.  If the first argument is neither a CV nor a GV, this flag is ignored
               (subject to change).

                       SV *    cv_name(CV *cv, SV *sv, U32 flags)

       cv_undef
               Clear out all the active components of a CV.  This can happen either by an
               explicit "undef &foo", or by the reference count going to zero.  In the former
               case, we keep the "CvOUTSIDE" pointer, so that any anonymous children can still
               follow the full lexical scope chain.

                       void    cv_undef(CV* cv)

       find_rundefsv
               Returns the global variable $_.

                       SV *    find_rundefsv()

       find_rundefsvoffset
               DEPRECATED!  It is planned to remove this function from a future release of Perl.
               Do not use it for new code; remove it from existing code.

               Until the lexical $_ feature was removed, this function would find the position of
               the lexical $_ in the pad of the currently-executing function and returns the
               offset in the current pad, or "NOT_IN_PAD".

               Now it always returns "NOT_IN_PAD".

               NOTE: the perl_ form of this function is deprecated.

                       PADOFFSET find_rundefsvoffset()

       intro_my
               "Introduce" "my" variables to visible status.  This is called during parsing at
               the end of each statement to make lexical variables visible to subsequent
               statements.

                       U32     intro_my()

       load_module
               Loads the module whose name is pointed to by the string part of "name".  Note that
               the actual module name, not its filename, should be given.  Eg, "Foo::Bar" instead
               of "Foo/Bar.pm". ver, if specified and not NULL, provides version semantics
               similar to "use Foo::Bar VERSION". The optional trailing arguments can be used to
               specify arguments to the module's "import()" method, similar to "use Foo::Bar
               VERSION LIST"; their precise handling depends on the flags. The flags argument is
               a bitwise-ORed collection of any of "PERL_LOADMOD_DENY", "PERL_LOADMOD_NOIMPORT",
               or "PERL_LOADMOD_IMPORT_OPS" (or 0 for no flags).

               If "PERL_LOADMOD_NOIMPORT" is set, the module is loaded as if with an empty import
               list, as in "use Foo::Bar ()"; this is the only circumstance in which the trailing
               optional arguments may be omitted entirely. Otherwise, if
               "PERL_LOADMOD_IMPORT_OPS" is set, the trailing arguments must consist of exactly
               one "OP*", containing the op tree that produces the relevant import arguments.
               Otherwise, the trailing arguments must all be "SV*" values that will be used as
               import arguments; and the list must be terminated with "(SV*) NULL". If neither
               "PERL_LOADMOD_NOIMPORT" nor "PERL_LOADMOD_IMPORT_OPS" is set, the trailing "NULL"
               pointer is needed even if no import arguments are desired. The reference count for
               each specified "SV*" argument is decremented. In addition, the "name" argument is
               modified.

               If "PERL_LOADMOD_DENY" is set, the module is loaded as if with "no" rather than
               "use".

                       void    load_module(U32 flags, SV* name, SV* ver, ...)

       newPADNAMELIST
               NOTE: this function is experimental and may change or be removed without notice.

               Creates a new pad name list.  "max" is the highest index for which space is
               allocated.

                       PADNAMELIST * newPADNAMELIST(size_t max)

       newPADNAMEouter
               NOTE: this function is experimental and may change or be removed without notice.

               Constructs and returns a new pad name.  Only use this function for names that
               refer to outer lexicals.  (See also "newPADNAMEpvn".)  "outer" is the outer pad
               name that this one mirrors.  The returned pad name has the "PADNAMEt_OUTER" flag
               already set.

                       PADNAME * newPADNAMEouter(PADNAME *outer)

       newPADNAMEpvn
               NOTE: this function is experimental and may change or be removed without notice.

               Constructs and returns a new pad name.  "s" must be a UTF-8 string.  Do not use
               this for pad names that point to outer lexicals.  See "newPADNAMEouter".

                       PADNAME * newPADNAMEpvn(const char *s, STRLEN len)

       nothreadhook
               Stub that provides thread hook for perl_destruct when there are no threads.

                       int     nothreadhook()

       pad_add_anon
               Allocates a place in the currently-compiling pad (via "pad_alloc") for an
               anonymous function that is lexically scoped inside the currently-compiling
               function.  The function "func" is linked into the pad, and its "CvOUTSIDE" link to
               the outer scope is weakened to avoid a reference loop.

               One reference count is stolen, so you may need to do "SvREFCNT_inc(func)".

               "optype" should be an opcode indicating the type of operation that the pad entry
               is to support.  This doesn't affect operational semantics, but is used for
               debugging.

                       PADOFFSET pad_add_anon(CV *func, I32 optype)

       pad_add_name_pv
               Exactly like "pad_add_name_pvn", but takes a nul-terminated string instead of a
               string/length pair.

                       PADOFFSET pad_add_name_pv(const char *name, U32 flags,
                                                 HV *typestash, HV *ourstash)

       pad_add_name_pvn
               Allocates a place in the currently-compiling pad for a named lexical variable.
               Stores the name and other metadata in the name part of the pad, and makes
               preparations to manage the variable's lexical scoping.  Returns the offset of the
               allocated pad slot.

               "namepv"/"namelen" specify the variable's name, including leading sigil.  If
               "typestash" is non-null, the name is for a typed lexical, and this identifies the
               type.  If "ourstash" is non-null, it's a lexical reference to a package variable,
               and this identifies the package.  The following flags can be OR'ed together:

                padadd_OUR          redundantly specifies if it's a package var
                padadd_STATE        variable will retain value persistently
                padadd_NO_DUP_CHECK skip check for lexical shadowing

                       PADOFFSET pad_add_name_pvn(const char *namepv,
                                                  STRLEN namelen, U32 flags,
                                                  HV *typestash, HV *ourstash)

       pad_add_name_sv
               Exactly like "pad_add_name_pvn", but takes the name string in the form of an SV
               instead of a string/length pair.

                       PADOFFSET pad_add_name_sv(SV *name, U32 flags,
                                                 HV *typestash, HV *ourstash)

       pad_alloc
               NOTE: this function is experimental and may change or be removed without notice.

               Allocates a place in the currently-compiling pad, returning the offset of the
               allocated pad slot.  No name is initially attached to the pad slot.  "tmptype" is
               a set of flags indicating the kind of pad entry required, which will be set in the
               value SV for the allocated pad entry:

                   SVs_PADMY    named lexical variable ("my", "our", "state")
                   SVs_PADTMP   unnamed temporary store
                   SVf_READONLY constant shared between recursion levels

               "SVf_READONLY" has been supported here only since perl 5.20.  To work with earlier
               versions as well, use "SVf_READONLY|SVs_PADTMP".  "SVf_READONLY" does not cause
               the SV in the pad slot to be marked read-only, but simply tells "pad_alloc" that
               it will be made read-only (by the caller), or at least should be treated as such.

               "optype" should be an opcode indicating the type of operation that the pad entry
               is to support.  This doesn't affect operational semantics, but is used for
               debugging.

                       PADOFFSET pad_alloc(I32 optype, U32 tmptype)

       pad_findmy_pv
               Exactly like "pad_findmy_pvn", but takes a nul-terminated string instead of a
               string/length pair.

                       PADOFFSET pad_findmy_pv(const char *name, U32 flags)

       pad_findmy_pvn
               Given the name of a lexical variable, find its position in the currently-compiling
               pad.  "namepv"/"namelen" specify the variable's name, including leading sigil.
               "flags" is reserved and must be zero.  If it is not in the current pad but appears
               in the pad of any lexically enclosing scope, then a pseudo-entry for it is added
               in the current pad.  Returns the offset in the current pad, or "NOT_IN_PAD" if no
               such lexical is in scope.

                       PADOFFSET pad_findmy_pvn(const char *namepv,
                                                STRLEN namelen, U32 flags)

       pad_findmy_sv
               Exactly like "pad_findmy_pvn", but takes the name string in the form of an SV
               instead of a string/length pair.

                       PADOFFSET pad_findmy_sv(SV *name, U32 flags)

       padnamelist_fetch
               NOTE: this function is experimental and may change or be removed without notice.

               Fetches the pad name from the given index.

                       PADNAME * padnamelist_fetch(PADNAMELIST *pnl,
                                                   SSize_t key)

       padnamelist_store
               NOTE: this function is experimental and may change or be removed without notice.

               Stores the pad name (which may be null) at the given index, freeing any existing
               pad name in that slot.

                       PADNAME ** padnamelist_store(PADNAMELIST *pnl,
                                                    SSize_t key, PADNAME *val)

       pad_setsv
               Set the value at offset "po" in the current (compiling or executing) pad.  Use the
               macro "PAD_SETSV()" rather than calling this function directly.

                       void    pad_setsv(PADOFFSET po, SV *sv)

       pad_sv  Get the value at offset "po" in the current (compiling or executing) pad.  Use
               macro "PAD_SV" instead of calling this function directly.

                       SV *    pad_sv(PADOFFSET po)

       pad_tidy
               NOTE: this function is experimental and may change or be removed without notice.

               Tidy up a pad at the end of compilation of the code to which it belongs.  Jobs
               performed here are: remove most stuff from the pads of anonsub prototypes; give it
               a @_; mark temporaries as such.  "type" indicates the kind of subroutine:

                   padtidy_SUB        ordinary subroutine
                   padtidy_SUBCLONE   prototype for lexical closure
                   padtidy_FORMAT     format

                       void    pad_tidy(padtidy_type type)

       perl_alloc
               Allocates a new Perl interpreter.  See perlembed.

                       PerlInterpreter* perl_alloc()

       perl_construct
               Initializes a new Perl interpreter.  See perlembed.

                       void    perl_construct(PerlInterpreter *my_perl)

       perl_destruct
               Shuts down a Perl interpreter.  See perlembed.

                       int     perl_destruct(PerlInterpreter *my_perl)

       perl_free
               Releases a Perl interpreter.  See perlembed.

                       void    perl_free(PerlInterpreter *my_perl)

       perl_parse
               Tells a Perl interpreter to parse a Perl script.  See perlembed.

                       int     perl_parse(PerlInterpreter *my_perl,
                                          XSINIT_t xsinit, int argc,
                                          char** argv, char** env)

       perl_run
               Tells a Perl interpreter to run.  See perlembed.

                       int     perl_run(PerlInterpreter *my_perl)

       require_pv
               Tells Perl to "require" the file named by the string argument.  It is analogous to
               the Perl code "eval "require '$file'"".  It's even implemented that way; consider
               using load_module instead.

               NOTE: the perl_ form of this function is deprecated.

                       void    require_pv(const char* pv)

Exception Handling (simple) Macros

       dXCPT   Set up necessary local variables for exception handling.  See "Exception Handling"
               in perlguts.

                               dXCPT;

       XCPT_CATCH
               Introduces a catch block.  See "Exception Handling" in perlguts.

       XCPT_RETHROW
               Rethrows a previously caught exception.  See "Exception Handling" in perlguts.

                               XCPT_RETHROW;

       XCPT_TRY_END
               Ends a try block.  See "Exception Handling" in perlguts.

       XCPT_TRY_START
               Starts a try block.  See "Exception Handling" in perlguts.

Functions in file scope.c

       save_gp Saves the current GP of gv on the save stack to be restored on scope exit.

               If empty is true, replace the GP with a new GP.

               If empty is false, mark gv with GVf_INTRO so the next reference assigned is
               localized, which is how " local *foo = $someref; " works.

                       void    save_gp(GV* gv, I32 empty)

Functions in file vutil.c

       new_version
               Returns a new version object based on the passed in SV:

                   SV *sv = new_version(SV *ver);

               Does not alter the passed in ver SV.  See "upg_version" if you want to upgrade the
               SV.

                       SV*     new_version(SV *ver)

       prescan_version
               Validate that a given string can be parsed as a version object, but doesn't
               actually perform the parsing.  Can use either strict or lax validation rules.  Can
               optionally set a number of hint variables to save the parsing code some time when
               tokenizing.

                       const char* prescan_version(const char *s, bool strict,
                                                   const char** errstr,
                                                   bool *sqv,
                                                   int *ssaw_decimal,
                                                   int *swidth, bool *salpha)

       scan_version
               Returns a pointer to the next character after the parsed version string, as well
               as upgrading the passed in SV to an RV.

               Function must be called with an already existing SV like

                   sv = newSV(0);
                   s = scan_version(s, SV *sv, bool qv);

               Performs some preprocessing to the string to ensure that it has the correct
               characteristics of a version.  Flags the object if it contains an underscore
               (which denotes this is an alpha version).  The boolean qv denotes that the version
               should be interpreted as if it had multiple decimals, even if it doesn't.

                       const char* scan_version(const char *s, SV *rv, bool qv)

       upg_version
               In-place upgrade of the supplied SV to a version object.

                   SV *sv = upg_version(SV *sv, bool qv);

               Returns a pointer to the upgraded SV.  Set the boolean qv if you want to force
               this SV to be interpreted as an "extended" version.

                       SV*     upg_version(SV *ver, bool qv)

       vcmp    Version object aware cmp.  Both operands must already have been converted into
               version objects.

                       int     vcmp(SV *lhv, SV *rhv)

       vnormal Accepts a version object and returns the normalized string representation.  Call
               like:

                   sv = vnormal(rv);

               NOTE: you can pass either the object directly or the SV contained within the RV.

               The SV returned has a refcount of 1.

                       SV*     vnormal(SV *vs)

       vnumify Accepts a version object and returns the normalized floating point representation.
               Call like:

                   sv = vnumify(rv);

               NOTE: you can pass either the object directly or the SV contained within the RV.

               The SV returned has a refcount of 1.

                       SV*     vnumify(SV *vs)

       vstringify
               In order to maintain maximum compatibility with earlier versions of Perl, this
               function will return either the floating point notation or the multiple dotted
               notation, depending on whether the original version contained 1 or more dots,
               respectively.

               The SV returned has a refcount of 1.

                       SV*     vstringify(SV *vs)

       vverify Validates that the SV contains valid internal structure for a version object.  It
               may be passed either the version object (RV) or the hash itself (HV).  If the
               structure is valid, it returns the HV.  If the structure is invalid, it returns
               NULL.

                   SV *hv = vverify(sv);

               Note that it only confirms the bare minimum structure (so as not to get confused
               by derived classes which may contain additional hash entries):

               ·   The SV is an HV or a reference to an HV

               ·   The hash contains a "version" key

               ·   The "version" key has a reference to an AV as its value

                       SV*     vverify(SV *vs)

"Gimme" Values

       G_ARRAY Used to indicate list context.  See "GIMME_V", "GIMME" and perlcall.

       G_DISCARD
               Indicates that arguments returned from a callback should be discarded.  See
               perlcall.

       G_EVAL  Used to force a Perl "eval" wrapper around a callback.  See perlcall.

       GIMME   A backward-compatible version of "GIMME_V" which can only return "G_SCALAR" or
               "G_ARRAY"; in a void context, it returns "G_SCALAR".  Deprecated.  Use "GIMME_V"
               instead.

                       U32     GIMME

       GIMME_V The XSUB-writer's equivalent to Perl's "wantarray".  Returns "G_VOID", "G_SCALAR"
               or "G_ARRAY" for void, scalar or list context, respectively.  See perlcall for a
               usage example.

                       U32     GIMME_V

       G_NOARGS
               Indicates that no arguments are being sent to a callback.  See perlcall.

       G_SCALAR
               Used to indicate scalar context.  See "GIMME_V", "GIMME", and perlcall.

       G_VOID  Used to indicate void context.  See "GIMME_V" and perlcall.

Global Variables

       These variables are global to an entire process.  They are shared between all interpreters
       and all threads in a process.  Any variables not documented here may be changed or removed
       without notice, so don't use them!  If you feel you really do need to use an unlisted
       variable, first send email to perl5-porters@perl.org <mailto:perl5-porters@perl.org>.  It
       may be that someone there will point out a way to accomplish what you need without using
       an internal variable.  But if not, you should get a go-ahead to document and then use the
       variable.

       PL_check
               Array, indexed by opcode, of functions that will be called for the "check" phase
               of optree building during compilation of Perl code.  For most (but not all) types
               of op, once the op has been initially built and populated with child ops it will
               be filtered through the check function referenced by the appropriate element of
               this array.  The new op is passed in as the sole argument to the check function,
               and the check function returns the completed op.  The check function may (as the
               name suggests) check the op for validity and signal errors.  It may also
               initialise or modify parts of the ops, or perform more radical surgery such as
               adding or removing child ops, or even throw the op away and return a different op
               in its place.

               This array of function pointers is a convenient place to hook into the compilation
               process.  An XS module can put its own custom check function in place of any of
               the standard ones, to influence the compilation of a particular type of op.
               However, a custom check function must never fully replace a standard check
               function (or even a custom check function from another module).  A module
               modifying checking must instead wrap the preexisting check function.  A custom
               check function must be selective about when to apply its custom behaviour.  In the
               usual case where it decides not to do anything special with an op, it must chain
               the preexisting op function.  Check functions are thus linked in a chain, with the
               core's base checker at the end.

               For thread safety, modules should not write directly to this array.  Instead, use
               the function "wrap_op_checker".

       PL_keyword_plugin
               NOTE: this function is experimental and may change or be removed without notice.

               Function pointer, pointing at a function used to handle extended keywords.  The
               function should be declared as

                       int keyword_plugin_function(pTHX_
                               char *keyword_ptr, STRLEN keyword_len,
                               OP **op_ptr)

               The function is called from the tokeniser, whenever a possible keyword is seen.
               "keyword_ptr" points at the word in the parser's input buffer, and "keyword_len"
               gives its length; it is not null-terminated.  The function is expected to examine
               the word, and possibly other state such as %^H, to decide whether it wants to
               handle it as an extended keyword.  If it does not, the function should return
               "KEYWORD_PLUGIN_DECLINE", and the normal parser process will continue.

               If the function wants to handle the keyword, it first must parse anything
               following the keyword that is part of the syntax introduced by the keyword.  See
               "Lexer interface" for details.

               When a keyword is being handled, the plugin function must build a tree of "OP"
               structures, representing the code that was parsed.  The root of the tree must be
               stored in *op_ptr.  The function then returns a constant indicating the syntactic
               role of the construct that it has parsed: "KEYWORD_PLUGIN_STMT" if it is a
               complete statement, or "KEYWORD_PLUGIN_EXPR" if it is an expression.  Note that a
               statement construct cannot be used inside an expression (except via "do BLOCK" and
               similar), and an expression is not a complete statement (it requires at least a
               terminating semicolon).

               When a keyword is handled, the plugin function may also have (compile-time) side
               effects.  It may modify "%^H", define functions, and so on.  Typically, if side
               effects are the main purpose of a handler, it does not wish to generate any ops to
               be included in the normal compilation.  In this case it is still required to
               supply an op tree, but it suffices to generate a single null op.

               That's how the *PL_keyword_plugin function needs to behave overall.
               Conventionally, however, one does not completely replace the existing handler
               function.  Instead, take a copy of "PL_keyword_plugin" before assigning your own
               function pointer to it.  Your handler function should look for keywords that it is
               interested in and handle those.  Where it is not interested, it should call the
               saved plugin function, passing on the arguments it received.  Thus
               "PL_keyword_plugin" actually points at a chain of handler functions, all of which
               have an opportunity to handle keywords, and only the last function in the chain
               (built into the Perl core) will normally return "KEYWORD_PLUGIN_DECLINE".

GV Functions

       A GV is a structure which corresponds to to a Perl typeglob, ie *foo.  It is a structure
       that holds a pointer to a scalar, an array, a hash etc, corresponding to $foo, @foo, %foo.

       GVs are usually found as values in stashes (symbol table hashes) where Perl stores its
       global variables.

       GvAV    Return the AV from the GV.

                       AV*     GvAV(GV* gv)

       gv_const_sv
               If "gv" is a typeglob whose subroutine entry is a constant sub eligible for
               inlining, or "gv" is a placeholder reference that would be promoted to such a
               typeglob, then returns the value returned by the sub.  Otherwise, returns "NULL".

                       SV*     gv_const_sv(GV* gv)

       GvCV    Return the CV from the GV.

                       CV*     GvCV(GV* gv)

       gv_fetchmeth
               Like "gv_fetchmeth_pvn", but lacks a flags parameter.

                       GV*     gv_fetchmeth(HV* stash, const char* name,
                                            STRLEN len, I32 level)

       gv_fetchmethod_autoload
               Returns the glob which contains the subroutine to call to invoke the method on the
               "stash".  In fact in the presence of autoloading this may be the glob for
               "AUTOLOAD".  In this case the corresponding variable $AUTOLOAD is already setup.

               The third parameter of "gv_fetchmethod_autoload" determines whether AUTOLOAD
               lookup is performed if the given method is not present: non-zero means yes, look
               for AUTOLOAD; zero means no, don't look for AUTOLOAD.  Calling "gv_fetchmethod" is
               equivalent to calling "gv_fetchmethod_autoload" with a non-zero "autoload"
               parameter.

               These functions grant "SUPER" token as a prefix of the method name.  Note that if
               you want to keep the returned glob for a long time, you need to check for it being
               "AUTOLOAD", since at the later time the call may load a different subroutine due
               to $AUTOLOAD changing its value.  Use the glob created as a side effect to do
               this.

               These functions have the same side-effects as "gv_fetchmeth" with "level==0".  The
               warning against passing the GV returned by "gv_fetchmeth" to "call_sv" applies
               equally to these functions.

                       GV*     gv_fetchmethod_autoload(HV* stash,
                                                       const char* name,
                                                       I32 autoload)

       gv_fetchmeth_autoload
               This is the old form of "gv_fetchmeth_pvn_autoload", which has no flags parameter.

                       GV*     gv_fetchmeth_autoload(HV* stash,
                                                     const char* name,
                                                     STRLEN len, I32 level)

       gv_fetchmeth_pv
               Exactly like "gv_fetchmeth_pvn", but takes a nul-terminated string instead of a
               string/length pair.

                       GV*     gv_fetchmeth_pv(HV* stash, const char* name,
                                               I32 level, U32 flags)

       gv_fetchmeth_pvn
               Returns the glob with the given "name" and a defined subroutine or "NULL".  The
               glob lives in the given "stash", or in the stashes accessible via @ISA and
               "UNIVERSAL::".

               The argument "level" should be either 0 or -1.  If "level==0", as a side-effect
               creates a glob with the given "name" in the given "stash" which in the case of
               success contains an alias for the subroutine, and sets up caching info for this
               glob.

               The only significant values for "flags" are "GV_SUPER" and "SVf_UTF8".

               "GV_SUPER" indicates that we want to look up the method in the superclasses of the
               "stash".

               The GV returned from "gv_fetchmeth" may be a method cache entry, which is not
               visible to Perl code.  So when calling "call_sv", you should not use the GV
               directly; instead, you should use the method's CV, which can be obtained from the
               GV with the "GvCV" macro.

                       GV*     gv_fetchmeth_pvn(HV* stash, const char* name,
                                                STRLEN len, I32 level,
                                                U32 flags)

       gv_fetchmeth_pvn_autoload
               Same as "gv_fetchmeth_pvn()", but looks for autoloaded subroutines too.  Returns a
               glob for the subroutine.

               For an autoloaded subroutine without a GV, will create a GV even if "level < 0".
               For an autoloaded subroutine without a stub, "GvCV()" of the result may be zero.

               Currently, the only significant value for "flags" is "SVf_UTF8".

                       GV*     gv_fetchmeth_pvn_autoload(HV* stash,
                                                         const char* name,
                                                         STRLEN len, I32 level,
                                                         U32 flags)

       gv_fetchmeth_pv_autoload
               Exactly like "gv_fetchmeth_pvn_autoload", but takes a nul-terminated string
               instead of a string/length pair.

                       GV*     gv_fetchmeth_pv_autoload(HV* stash,
                                                        const char* name,
                                                        I32 level, U32 flags)

       gv_fetchmeth_sv
               Exactly like "gv_fetchmeth_pvn", but takes the name string in the form of an SV
               instead of a string/length pair.

                       GV*     gv_fetchmeth_sv(HV* stash, SV* namesv,
                                               I32 level, U32 flags)

       gv_fetchmeth_sv_autoload
               Exactly like "gv_fetchmeth_pvn_autoload", but takes the name string in the form of
               an SV instead of a string/length pair.

                       GV*     gv_fetchmeth_sv_autoload(HV* stash, SV* namesv,
                                                        I32 level, U32 flags)

       GvHV    Return the HV from the GV.

                       HV*     GvHV(GV* gv)

       gv_init The old form of "gv_init_pvn()".  It does not work with UTF-8 strings, as it has
               no flags parameter.  If the "multi" parameter is set, the "GV_ADDMULTI" flag will
               be passed to "gv_init_pvn()".

                       void    gv_init(GV* gv, HV* stash, const char* name,
                                       STRLEN len, int multi)

       gv_init_pv
               Same as "gv_init_pvn()", but takes a nul-terminated string for the name instead of
               separate char * and length parameters.

                       void    gv_init_pv(GV* gv, HV* stash, const char* name,
                                          U32 flags)

       gv_init_pvn
               Converts a scalar into a typeglob.  This is an incoercible typeglob; assigning a
               reference to it will assign to one of its slots, instead of overwriting it as
               happens with typeglobs created by "SvSetSV".  Converting any scalar that is
               "SvOK()" may produce unpredictable results and is reserved for perl's internal
               use.

               "gv" is the scalar to be converted.

               "stash" is the parent stash/package, if any.

               "name" and "len" give the name.  The name must be unqualified; that is, it must
               not include the package name.  If "gv" is a stash element, it is the caller's
               responsibility to ensure that the name passed to this function matches the name of
               the element.  If it does not match, perl's internal bookkeeping will get out of
               sync.

               "flags" can be set to "SVf_UTF8" if "name" is a UTF-8 string, or the return value
               of SvUTF8(sv).  It can also take the "GV_ADDMULTI" flag, which means to pretend
               that the GV has been seen before (i.e., suppress "Used once" warnings).

                       void    gv_init_pvn(GV* gv, HV* stash, const char* name,
                                           STRLEN len, U32 flags)

       gv_init_sv
               Same as "gv_init_pvn()", but takes an SV * for the name instead of separate char *
               and length parameters.  "flags" is currently unused.

                       void    gv_init_sv(GV* gv, HV* stash, SV* namesv,
                                          U32 flags)

       gv_stashpv
               Returns a pointer to the stash for a specified package.  Uses "strlen" to
               determine the length of "name", then calls "gv_stashpvn()".

                       HV*     gv_stashpv(const char* name, I32 flags)

       gv_stashpvn
               Returns a pointer to the stash for a specified package.  The "namelen" parameter
               indicates the length of the "name", in bytes.  "flags" is passed to
               "gv_fetchpvn_flags()", so if set to "GV_ADD" then the package will be created if
               it does not already exist.  If the package does not exist and "flags" is 0 (or any
               other setting that does not create packages) then "NULL" is returned.

               Flags may be one of:

                   GV_ADD
                   SVf_UTF8
                   GV_NOADD_NOINIT
                   GV_NOINIT
                   GV_NOEXPAND
                   GV_ADDMG

               The most important of which are probably "GV_ADD" and "SVf_UTF8".

               Note, use of "gv_stashsv" instead of "gv_stashpvn" where possible is strongly
               recommended for performance reasons.

                       HV*     gv_stashpvn(const char* name, U32 namelen,
                                           I32 flags)

       gv_stashpvs
               Like "gv_stashpvn", but takes a "NUL"-terminated literal string instead of a
               string/length pair.

                       HV*     gv_stashpvs(const char* name, I32 create)

       gv_stashsv
               Returns a pointer to the stash for a specified package.  See "gv_stashpvn".

               Note this interface is strongly preferred over "gv_stashpvn" for performance
               reasons.

                       HV*     gv_stashsv(SV* sv, I32 flags)

       GvSV    Return the SV from the GV.

                       SV*     GvSV(GV* gv)

       setdefout
               Sets "PL_defoutgv", the default file handle for output, to the passed in typeglob.
               As "PL_defoutgv" "owns" a reference on its typeglob, the reference count of the
               passed in typeglob is increased by one, and the reference count of the typeglob
               that "PL_defoutgv" points to is decreased by one.

                       void    setdefout(GV* gv)

Handy Values

       Nullav  Null AV pointer.

               (deprecated - use "(AV *)NULL" instead)

       Nullch  Null character pointer.  (No longer available when "PERL_CORE" is defined.)

       Nullcv  Null CV pointer.

               (deprecated - use "(CV *)NULL" instead)

       Nullhv  Null HV pointer.

               (deprecated - use "(HV *)NULL" instead)

       Nullsv  Null SV pointer.  (No longer available when "PERL_CORE" is defined.)

Hash Manipulation Functions

       A HV structure represents a Perl hash.  It consists mainly of an array of pointers, each
       of which points to a linked list of HE structures.  The array is indexed by the hash
       function of the key, so each linked list represents all the hash entries with the same
       hash value.  Each HE contains a pointer to the actual value, plus a pointer to a HEK
       structure which holds the key and hash value.

       cop_fetch_label
               NOTE: this function is experimental and may change or be removed without notice.

               Returns the label attached to a cop.  The flags pointer may be set to "SVf_UTF8"
               or 0.

                       const char * cop_fetch_label(COP *const cop,
                                                    STRLEN *len, U32 *flags)

       cop_store_label
               NOTE: this function is experimental and may change or be removed without notice.

               Save a label into a "cop_hints_hash".  You need to set flags to "SVf_UTF8" for a
               UTF-8 label.

                       void    cop_store_label(COP *const cop,
                                               const char *label, STRLEN len,
                                               U32 flags)

       get_hv  Returns the HV of the specified Perl hash.  "flags" are passed to "gv_fetchpv".
               If "GV_ADD" is set and the Perl variable does not exist then it will be created.
               If "flags" is zero and the variable does not exist then "NULL" is returned.

               NOTE: the perl_ form of this function is deprecated.

                       HV*     get_hv(const char *name, I32 flags)

       HEf_SVKEY
               This flag, used in the length slot of hash entries and magic structures, specifies
               the structure contains an "SV*" pointer where a "char*" pointer is to be expected.
               (For information only--not to be used).

       HeHASH  Returns the computed hash stored in the hash entry.

                       U32     HeHASH(HE* he)

       HeKEY   Returns the actual pointer stored in the key slot of the hash entry.  The pointer
               may be either "char*" or "SV*", depending on the value of "HeKLEN()".  Can be
               assigned to.  The "HePV()" or "HeSVKEY()" macros are usually preferable for
               finding the value of a key.

                       void*   HeKEY(HE* he)

       HeKLEN  If this is negative, and amounts to "HEf_SVKEY", it indicates the entry holds an
               "SV*" key.  Otherwise, holds the actual length of the key.  Can be assigned to.
               The "HePV()" macro is usually preferable for finding key lengths.

                       STRLEN  HeKLEN(HE* he)

       HePV    Returns the key slot of the hash entry as a "char*" value, doing any necessary
               dereferencing of possibly "SV*" keys.  The length of the string is placed in "len"
               (this is a macro, so do not use &len).  If you do not care about what the length
               of the key is, you may use the global variable "PL_na", though this is rather less
               efficient than using a local variable.  Remember though, that hash keys in perl
               are free to contain embedded nulls, so using "strlen()" or similar is not a good
               way to find the length of hash keys.  This is very similar to the "SvPV()" macro
               described elsewhere in this document.  See also "HeUTF8".

               If you are using "HePV" to get values to pass to "newSVpvn()" to create a new SV,
               you should consider using "newSVhek(HeKEY_hek(he))" as it is more efficient.

                       char*   HePV(HE* he, STRLEN len)

       HeSVKEY Returns the key as an "SV*", or "NULL" if the hash entry does not contain an "SV*"
               key.

                       SV*     HeSVKEY(HE* he)

       HeSVKEY_force
               Returns the key as an "SV*".  Will create and return a temporary mortal "SV*" if
               the hash entry contains only a "char*" key.

                       SV*     HeSVKEY_force(HE* he)

       HeSVKEY_set
               Sets the key to a given "SV*", taking care to set the appropriate flags to
               indicate the presence of an "SV*" key, and returns the same "SV*".

                       SV*     HeSVKEY_set(HE* he, SV* sv)

       HeUTF8  Returns whether the "char *" value returned by "HePV" is encoded in UTF-8, doing
               any necessary dereferencing of possibly "SV*" keys.  The value returned will be 0
               or non-0, not necessarily 1 (or even a value with any low bits set), so do not
               blindly assign this to a "bool" variable, as "bool" may be a typedef for "char".

                       U32     HeUTF8(HE* he)

       HeVAL   Returns the value slot (type "SV*") stored in the hash entry.  Can be assigned to.

                 SV *foo= HeVAL(hv);
                 HeVAL(hv)= sv;

                       SV*     HeVAL(HE* he)

       hv_assert
               Check that a hash is in an internally consistent state.

                       void    hv_assert(HV *hv)

       hv_bucket_ratio
               NOTE: this function is experimental and may change or be removed without notice.

               If the hash is tied dispatches through to the SCALAR tied method, otherwise if the
               hash contains no keys returns 0, otherwise returns a mortal sv containing a string
               specifying the number of used buckets, followed by a slash, followed by the number
               of available buckets.

               This function is expensive, it must scan all of the buckets to determine which are
               used, and the count is NOT cached.  In a large hash this could be a lot of
               buckets.

                       SV*     hv_bucket_ratio(HV *hv)

       hv_clear
               Frees the all the elements of a hash, leaving it empty.  The XS equivalent of
               "%hash = ()".  See also "hv_undef".

               See "av_clear" for a note about the hash possibly being invalid on return.

                       void    hv_clear(HV *hv)

       hv_clear_placeholders
               Clears any placeholders from a hash.  If a restricted hash has any of its keys
               marked as readonly and the key is subsequently deleted, the key is not actually
               deleted but is marked by assigning it a value of &PL_sv_placeholder.  This tags it
               so it will be ignored by future operations such as iterating over the hash, but
               will still allow the hash to have a value reassigned to the key at some future
               point.  This function clears any such placeholder keys from the hash.  See
               "Hash::Util::lock_keys()" for an example of its use.

                       void    hv_clear_placeholders(HV *hv)

       hv_copy_hints_hv
               A specialised version of "newHVhv" for copying "%^H".  "ohv" must be a pointer to
               a hash (which may have "%^H" magic, but should be generally non-magical), or
               "NULL" (interpreted as an empty hash).  The content of "ohv" is copied to a new
               hash, which has the "%^H"-specific magic added to it.  A pointer to the new hash
               is returned.

                       HV *    hv_copy_hints_hv(HV *ohv)

       hv_delete
               Deletes a key/value pair in the hash.  The value's SV is removed from the hash,
               made mortal, and returned to the caller.  The absolute value of "klen" is the
               length of the key.  If "klen" is negative the key is assumed to be in
               UTF-8-encoded Unicode.  The "flags" value will normally be zero; if set to
               "G_DISCARD" then "NULL" will be returned.  "NULL" will also be returned if the key
               is not found.

                       SV*     hv_delete(HV *hv, const char *key, I32 klen,
                                         I32 flags)

       hv_delete_ent
               Deletes a key/value pair in the hash.  The value SV is removed from the hash, made
               mortal, and returned to the caller.  The "flags" value will normally be zero; if
               set to "G_DISCARD" then "NULL" will be returned.  "NULL" will also be returned if
               the key is not found.  "hash" can be a valid precomputed hash value, or 0 to ask
               for it to be computed.

                       SV*     hv_delete_ent(HV *hv, SV *keysv, I32 flags,
                                             U32 hash)

       HvENAME Returns the effective name of a stash, or NULL if there is none.  The effective
               name represents a location in the symbol table where this stash resides.  It is
               updated automatically when packages are aliased or deleted.  A stash that is no
               longer in the symbol table has no effective name.  This name is preferable to
               "HvNAME" for use in MRO linearisations and isa caches.

                       char*   HvENAME(HV* stash)

       HvENAMELEN
               Returns the length of the stash's effective name.

                       STRLEN  HvENAMELEN(HV *stash)

       HvENAMEUTF8
               Returns true if the effective name is in UTF-8 encoding.

                       unsigned char HvENAMEUTF8(HV *stash)

       hv_exists
               Returns a boolean indicating whether the specified hash key exists.  The absolute
               value of "klen" is the length of the key.  If "klen" is negative the key is
               assumed to be in UTF-8-encoded Unicode.

                       bool    hv_exists(HV *hv, const char *key, I32 klen)

       hv_exists_ent
               Returns a boolean indicating whether the specified hash key exists.  "hash" can be
               a valid precomputed hash value, or 0 to ask for it to be computed.

                       bool    hv_exists_ent(HV *hv, SV *keysv, U32 hash)

       hv_fetch
               Returns the SV which corresponds to the specified key in the hash.  The absolute
               value of "klen" is the length of the key.  If "klen" is negative the key is
               assumed to be in UTF-8-encoded Unicode.  If "lval" is set then the fetch will be
               part of a store.  This means that if there is no value in the hash associated with
               the given key, then one is created and a pointer to it is returned.  The "SV*" it
               points to can be assigned to.  But always check that the return value is non-null
               before dereferencing it to an "SV*".

               See "Understanding the Magic of Tied Hashes and Arrays" in perlguts for more
               information on how to use this function on tied hashes.

                       SV**    hv_fetch(HV *hv, const char *key, I32 klen,
                                        I32 lval)

       hv_fetchs
               Like "hv_fetch", but takes a "NUL"-terminated literal string instead of a
               string/length pair.

                       SV**    hv_fetchs(HV* tb, const char* key, I32 lval)

       hv_fetch_ent
               Returns the hash entry which corresponds to the specified key in the hash.  "hash"
               must be a valid precomputed hash number for the given "key", or 0 if you want the
               function to compute it.  IF "lval" is set then the fetch will be part of a store.
               Make sure the return value is non-null before accessing it.  The return value when
               "hv" is a tied hash is a pointer to a static location, so be sure to make a copy
               of the structure if you need to store it somewhere.

               See "Understanding the Magic of Tied Hashes and Arrays" in perlguts for more
               information on how to use this function on tied hashes.

                       HE*     hv_fetch_ent(HV *hv, SV *keysv, I32 lval,
                                            U32 hash)

       hv_fill Returns the number of hash buckets that happen to be in use.

               This function is wrapped by the macro "HvFILL".

               As of perl 5.25 this function is used only for debugging purposes, and the number
               of used hash buckets is not in any way cached, thus this function can be costly to
               execute as it must iterate over all the buckets in the hash.

                       STRLEN  hv_fill(HV *const hv)

       hv_iterinit
               Prepares a starting point to traverse a hash table.  Returns the number of keys in
               the hash, including placeholders (i.e. the same as "HvTOTALKEYS(hv)").  The return
               value is currently only meaningful for hashes without tie magic.

               NOTE: Before version 5.004_65, "hv_iterinit" used to return the number of hash
               buckets that happen to be in use.  If you still need that esoteric value, you can
               get it through the macro "HvFILL(hv)".

                       I32     hv_iterinit(HV *hv)

       hv_iterkey
               Returns the key from the current position of the hash iterator.  See
               "hv_iterinit".

                       char*   hv_iterkey(HE* entry, I32* retlen)

       hv_iterkeysv
               Returns the key as an "SV*" from the current position of the hash iterator.  The
               return value will always be a mortal copy of the key.  Also see "hv_iterinit".

                       SV*     hv_iterkeysv(HE* entry)

       hv_iternext
               Returns entries from a hash iterator.  See "hv_iterinit".

               You may call "hv_delete" or "hv_delete_ent" on the hash entry that the iterator
               currently points to, without losing your place or invalidating your iterator.
               Note that in this case the current entry is deleted from the hash with your
               iterator holding the last reference to it.  Your iterator is flagged to free the
               entry on the next call to "hv_iternext", so you must not discard your iterator
               immediately else the entry will leak - call "hv_iternext" to trigger the resource
               deallocation.

                       HE*     hv_iternext(HV *hv)

       hv_iternextsv
               Performs an "hv_iternext", "hv_iterkey", and "hv_iterval" in one operation.

                       SV*     hv_iternextsv(HV *hv, char **key, I32 *retlen)

       hv_iternext_flags
               NOTE: this function is experimental and may change or be removed without notice.

               Returns entries from a hash iterator.  See "hv_iterinit" and "hv_iternext".  The
               "flags" value will normally be zero; if "HV_ITERNEXT_WANTPLACEHOLDERS" is set the
               placeholders keys (for restricted hashes) will be returned in addition to normal
               keys.  By default placeholders are automatically skipped over.  Currently a
               placeholder is implemented with a value that is &PL_sv_placeholder.  Note that the
               implementation of placeholders and restricted hashes may change, and the
               implementation currently is insufficiently abstracted for any change to be tidy.

                       HE*     hv_iternext_flags(HV *hv, I32 flags)

       hv_iterval
               Returns the value from the current position of the hash iterator.  See
               "hv_iterkey".

                       SV*     hv_iterval(HV *hv, HE *entry)

       hv_magic
               Adds magic to a hash.  See "sv_magic".

                       void    hv_magic(HV *hv, GV *gv, int how)

       HvNAME  Returns the package name of a stash, or "NULL" if "stash" isn't a stash.  See
               "SvSTASH", "CvSTASH".

                       char*   HvNAME(HV* stash)

       HvNAMELEN
               Returns the length of the stash's name.

                       STRLEN  HvNAMELEN(HV *stash)

       HvNAMEUTF8
               Returns true if the name is in UTF-8 encoding.

                       unsigned char HvNAMEUTF8(HV *stash)

       hv_scalar
               Evaluates the hash in scalar context and returns the result.

               When the hash is tied dispatches through to the SCALAR method, otherwise returns a
               mortal SV containing the number of keys in the hash.

               Note, prior to 5.25 this function returned what is now returned by the
               hv_bucket_ratio() function.

                       SV*     hv_scalar(HV *hv)

       hv_store
               Stores an SV in a hash.  The hash key is specified as "key" and the absolute value
               of "klen" is the length of the key.  If "klen" is negative the key is assumed to
               be in UTF-8-encoded Unicode.  The "hash" parameter is the precomputed hash value;
               if it is zero then Perl will compute it.

               The return value will be "NULL" if the operation failed or if the value did not
               need to be actually stored within the hash (as in the case of tied hashes).
               Otherwise it can be dereferenced to get the original "SV*".  Note that the caller
               is responsible for suitably incrementing the reference count of "val" before the
               call, and decrementing it if the function returned "NULL".  Effectively a
               successful "hv_store" takes ownership of one reference to "val".  This is usually
               what you want; a newly created SV has a reference count of one, so if all your
               code does is create SVs then store them in a hash, "hv_store" will own the only
               reference to the new SV, and your code doesn't need to do anything further to tidy
               up.  "hv_store" is not implemented as a call to "hv_store_ent", and does not
               create a temporary SV for the key, so if your key data is not already in SV form
               then use "hv_store" in preference to "hv_store_ent".

               See "Understanding the Magic of Tied Hashes and Arrays" in perlguts for more
               information on how to use this function on tied hashes.

                       SV**    hv_store(HV *hv, const char *key, I32 klen,
                                        SV *val, U32 hash)

       hv_stores
               Like "hv_store", but takes a "NUL"-terminated literal string instead of a
               string/length pair and omits the hash parameter.

                       SV**    hv_stores(HV* tb, const char* key,
                                         NULLOK SV* val)

       hv_store_ent
               Stores "val" in a hash.  The hash key is specified as "key".  The "hash" parameter
               is the precomputed hash value; if it is zero then Perl will compute it.  The
               return value is the new hash entry so created.  It will be "NULL" if the operation
               failed or if the value did not need to be actually stored within the hash (as in
               the case of tied hashes).  Otherwise the contents of the return value can be
               accessed using the "He?" macros described here.  Note that the caller is
               responsible for suitably incrementing the reference count of "val" before the
               call, and decrementing it if the function returned NULL.  Effectively a successful
               "hv_store_ent" takes ownership of one reference to "val".  This is usually what
               you want; a newly created SV has a reference count of one, so if all your code
               does is create SVs then store them in a hash, "hv_store" will own the only
               reference to the new SV, and your code doesn't need to do anything further to tidy
               up.  Note that "hv_store_ent" only reads the "key"; unlike "val" it does not take
               ownership of it, so maintaining the correct reference count on "key" is entirely
               the caller's responsibility.  "hv_store" is not implemented as a call to
               "hv_store_ent", and does not create a temporary SV for the key, so if your key
               data is not already in SV form then use "hv_store" in preference to
               "hv_store_ent".

               See "Understanding the Magic of Tied Hashes and Arrays" in perlguts for more
               information on how to use this function on tied hashes.

                       HE*     hv_store_ent(HV *hv, SV *key, SV *val, U32 hash)

       hv_undef
               Undefines the hash.  The XS equivalent of "undef(%hash)".

               As well as freeing all the elements of the hash (like "hv_clear()"), this also
               frees any auxiliary data and storage associated with the hash.

               See "av_clear" for a note about the hash possibly being invalid on return.

                       void    hv_undef(HV *hv)

       newHV   Creates a new HV.  The reference count is set to 1.

                       HV*     newHV()

Hook manipulation

       These functions provide convenient and thread-safe means of manipulating hook variables.

       wrap_op_checker
               Puts a C function into the chain of check functions for a specified op type.  This
               is the preferred way to manipulate the "PL_check" array.  "opcode" specifies which
               type of op is to be affected.  "new_checker" is a pointer to the C function that
               is to be added to that opcode's check chain, and "old_checker_p" points to the
               storage location where a pointer to the next function in the chain will be stored.
               The value of "new_pointer" is written into the "PL_check" array, while the value
               previously stored there is written to *old_checker_p.

               The function should be defined like this:

                   static OP *new_checker(pTHX_ OP *op) { ... }

               It is intended to be called in this manner:

                   new_checker(aTHX_ op)

               "old_checker_p" should be defined like this:

                   static Perl_check_t old_checker_p;

               "PL_check" is global to an entire process, and a module wishing to hook op
               checking may find itself invoked more than once per process, typically in
               different threads.  To handle that situation, this function is idempotent.  The
               location *old_checker_p must initially (once per process) contain a null pointer.
               A C variable of static duration (declared at file scope, typically also marked
               "static" to give it internal linkage) will be implicitly initialised
               appropriately, if it does not have an explicit initialiser.  This function will
               only actually modify the check chain if it finds *old_checker_p to be null.  This
               function is also thread safe on the small scale.  It uses appropriate locking to
               avoid race conditions in accessing "PL_check".

               When this function is called, the function referenced by "new_checker" must be
               ready to be called, except for *old_checker_p being unfilled.  In a threading
               situation, "new_checker" may be called immediately, even before this function has
               returned.  *old_checker_p will always be appropriately set before "new_checker" is
               called.  If "new_checker" decides not to do anything special with an op that it is
               given (which is the usual case for most uses of op check hooking), it must chain
               the check function referenced by *old_checker_p.

               If you want to influence compilation of calls to a specific subroutine, then use
               "cv_set_call_checker" rather than hooking checking of all "entersub" ops.

                       void    wrap_op_checker(Optype opcode,
                                               Perl_check_t new_checker,
                                               Perl_check_t *old_checker_p)

Lexer interface

       This is the lower layer of the Perl parser, managing characters and tokens.

       lex_bufutf8
               NOTE: this function is experimental and may change or be removed without notice.

               Indicates whether the octets in the lexer buffer ("PL_parser->linestr") should be
               interpreted as the UTF-8 encoding of Unicode characters.  If not, they should be
               interpreted as Latin-1 characters.  This is analogous to the "SvUTF8" flag for
               scalars.

               In UTF-8 mode, it is not guaranteed that the lexer buffer actually contains valid
               UTF-8.  Lexing code must be robust in the face of invalid encoding.

               The actual "SvUTF8" flag of the "PL_parser->linestr" scalar is significant, but
               not the whole story regarding the input character encoding.  Normally, when a file
               is being read, the scalar contains octets and its "SvUTF8" flag is off, but the
               octets should be interpreted as UTF-8 if the "use utf8" pragma is in effect.
               During a string eval, however, the scalar may have the "SvUTF8" flag on, and in
               this case its octets should be interpreted as UTF-8 unless the "use bytes" pragma
               is in effect.  This logic may change in the future; use this function instead of
               implementing the logic yourself.

                       bool    lex_bufutf8()

       lex_discard_to
               NOTE: this function is experimental and may change or be removed without notice.

               Discards the first part of the "PL_parser->linestr" buffer, up to "ptr".  The
               remaining content of the buffer will be moved, and all pointers into the buffer
               updated appropriately.  "ptr" must not be later in the buffer than the position of
               "PL_parser->bufptr": it is not permitted to discard text that has yet to be lexed.

               Normally it is not necessarily to do this directly, because it suffices to use the
               implicit discarding behaviour of "lex_next_chunk" and things based on it.
               However, if a token stretches across multiple lines, and the lexing code has kept
               multiple lines of text in the buffer for that purpose, then after completion of
               the token it would be wise to explicitly discard the now-unneeded earlier lines,
               to avoid future multi-line tokens growing the buffer without bound.

                       void    lex_discard_to(char *ptr)

       lex_grow_linestr
               NOTE: this function is experimental and may change or be removed without notice.

               Reallocates the lexer buffer ("PL_parser->linestr") to accommodate at least "len"
               octets (including terminating "NUL").  Returns a pointer to the reallocated
               buffer.  This is necessary before making any direct modification of the buffer
               that would increase its length.  "lex_stuff_pvn" provides a more convenient way to
               insert text into the buffer.

               Do not use "SvGROW" or "sv_grow" directly on "PL_parser->linestr"; this function
               updates all of the lexer's variables that point directly into the buffer.

                       char *  lex_grow_linestr(STRLEN len)

       lex_next_chunk
               NOTE: this function is experimental and may change or be removed without notice.

               Reads in the next chunk of text to be lexed, appending it to "PL_parser->linestr".
               This should be called when lexing code has looked to the end of the current chunk
               and wants to know more.  It is usual, but not necessary, for lexing to have
               consumed the entirety of the current chunk at this time.

               If "PL_parser->bufptr" is pointing to the very end of the current chunk (i.e., the
               current chunk has been entirely consumed), normally the current chunk will be
               discarded at the same time that the new chunk is read in.  If "flags" has the
               "LEX_KEEP_PREVIOUS" bit set, the current chunk will not be discarded.  If the
               current chunk has not been entirely consumed, then it will not be discarded
               regardless of the flag.

               Returns true if some new text was added to the buffer, or false if the buffer has
               reached the end of the input text.

                       bool    lex_next_chunk(U32 flags)

       lex_peek_unichar
               NOTE: this function is experimental and may change or be removed without notice.

               Looks ahead one (Unicode) character in the text currently being lexed.  Returns
               the codepoint (unsigned integer value) of the next character, or -1 if lexing has
               reached the end of the input text.  To consume the peeked character, use
               "lex_read_unichar".

               If the next character is in (or extends into) the next chunk of input text, the
               next chunk will be read in.  Normally the current chunk will be discarded at the
               same time, but if "flags" has the "LEX_KEEP_PREVIOUS" bit set, then the current
               chunk will not be discarded.

               If the input is being interpreted as UTF-8 and a UTF-8 encoding error is
               encountered, an exception is generated.

                       I32     lex_peek_unichar(U32 flags)

       lex_read_space
               NOTE: this function is experimental and may change or be removed without notice.

               Reads optional spaces, in Perl style, in the text currently being lexed.  The
               spaces may include ordinary whitespace characters and Perl-style comments.
               "#line" directives are processed if encountered.  "PL_parser->bufptr" is moved
               past the spaces, so that it points at a non-space character (or the end of the
               input text).

               If spaces extend into the next chunk of input text, the next chunk will be read
               in.  Normally the current chunk will be discarded at the same time, but if "flags"
               has the "LEX_KEEP_PREVIOUS" bit set, then the current chunk will not be discarded.

                       void    lex_read_space(U32 flags)

       lex_read_to
               NOTE: this function is experimental and may change or be removed without notice.

               Consume text in the lexer buffer, from "PL_parser->bufptr" up to "ptr".  This
               advances "PL_parser->bufptr" to match "ptr", performing the correct bookkeeping
               whenever a newline character is passed.  This is the normal way to consume lexed
               text.

               Interpretation of the buffer's octets can be abstracted out by using the slightly
               higher-level functions "lex_peek_unichar" and "lex_read_unichar".

                       void    lex_read_to(char *ptr)

       lex_read_unichar
               NOTE: this function is experimental and may change or be removed without notice.

               Reads the next (Unicode) character in the text currently being lexed.  Returns the
               codepoint (unsigned integer value) of the character read, and moves
               "PL_parser->bufptr" past the character, or returns -1 if lexing has reached the
               end of the input text.  To non-destructively examine the next character, use
               "lex_peek_unichar" instead.

               If the next character is in (or extends into) the next chunk of input text, the
               next chunk will be read in.  Normally the current chunk will be discarded at the
               same time, but if "flags" has the "LEX_KEEP_PREVIOUS" bit set, then the current
               chunk will not be discarded.

               If the input is being interpreted as UTF-8 and a UTF-8 encoding error is
               encountered, an exception is generated.

                       I32     lex_read_unichar(U32 flags)

       lex_start
               NOTE: this function is experimental and may change or be removed without notice.

               Creates and initialises a new lexer/parser state object, supplying a context in
               which to lex and parse from a new source of Perl code.  A pointer to the new state
               object is placed in "PL_parser".  An entry is made on the save stack so that upon
               unwinding, the new state object will be destroyed and the former value of
               "PL_parser" will be restored.  Nothing else need be done to clean up the parsing
               context.

               The code to be parsed comes from "line" and "rsfp".  "line", if non-null, provides
               a string (in SV form) containing code to be parsed.  A copy of the string is made,
               so subsequent modification of "line" does not affect parsing.  "rsfp", if non-
               null, provides an input stream from which code will be read to be parsed.  If both
               are non-null, the code in "line" comes first and must consist of complete lines of
               input, and "rsfp" supplies the remainder of the source.

               The "flags" parameter is reserved for future use.  Currently it is only used by
               perl internally, so extensions should always pass zero.

                       void    lex_start(SV *line, PerlIO *rsfp, U32 flags)

       lex_stuff_pv
               NOTE: this function is experimental and may change or be removed without notice.

               Insert characters into the lexer buffer ("PL_parser->linestr"), immediately after
               the current lexing point ("PL_parser->bufptr"), reallocating the buffer if
               necessary.  This means that lexing code that runs later will see the characters as
               if they had appeared in the input.  It is not recommended to do this as part of
               normal parsing, and most uses of this facility run the risk of the inserted
               characters being interpreted in an unintended manner.

               The string to be inserted is represented by octets starting at "pv" and continuing
               to the first nul.  These octets are interpreted as either UTF-8 or Latin-1,
               according to whether the "LEX_STUFF_UTF8" flag is set in "flags".  The characters
               are recoded for the lexer buffer, according to how the buffer is currently being
               interpreted ("lex_bufutf8").  If it is not convenient to nul-terminate a string to
               be inserted, the "lex_stuff_pvn" function is more appropriate.

                       void    lex_stuff_pv(const char *pv, U32 flags)

       lex_stuff_pvn
               NOTE: this function is experimental and may change or be removed without notice.

               Insert characters into the lexer buffer ("PL_parser->linestr"), immediately after
               the current lexing point ("PL_parser->bufptr"), reallocating the buffer if
               necessary.  This means that lexing code that runs later will see the characters as
               if they had appeared in the input.  It is not recommended to do this as part of
               normal parsing, and most uses of this facility run the risk of the inserted
               characters being interpreted in an unintended manner.

               The string to be inserted is represented by "len" octets starting at "pv".  These
               octets are interpreted as either UTF-8 or Latin-1, according to whether the
               "LEX_STUFF_UTF8" flag is set in "flags".  The characters are recoded for the lexer
               buffer, according to how the buffer is currently being interpreted
               ("lex_bufutf8").  If a string to be inserted is available as a Perl scalar, the
               "lex_stuff_sv" function is more convenient.

                       void    lex_stuff_pvn(const char *pv, STRLEN len,
                                             U32 flags)

       lex_stuff_pvs
               NOTE: this function is experimental and may change or be removed without notice.

               Like "lex_stuff_pvn", but takes a "NUL"-terminated literal string instead of a
               string/length pair.

                       void    lex_stuff_pvs(const char *pv, U32 flags)

       lex_stuff_sv
               NOTE: this function is experimental and may change or be removed without notice.

               Insert characters into the lexer buffer ("PL_parser->linestr"), immediately after
               the current lexing point ("PL_parser->bufptr"), reallocating the buffer if
               necessary.  This means that lexing code that runs later will see the characters as
               if they had appeared in the input.  It is not recommended to do this as part of
               normal parsing, and most uses of this facility run the risk of the inserted
               characters being interpreted in an unintended manner.

               The string to be inserted is the string value of "sv".  The characters are recoded
               for the lexer buffer, according to how the buffer is currently being interpreted
               ("lex_bufutf8").  If a string to be inserted is not already a Perl scalar, the
               "lex_stuff_pvn" function avoids the need to construct a scalar.

                       void    lex_stuff_sv(SV *sv, U32 flags)

       lex_unstuff
               NOTE: this function is experimental and may change or be removed without notice.

               Discards text about to be lexed, from "PL_parser->bufptr" up to "ptr".  Text
               following "ptr" will be moved, and the buffer shortened.  This hides the discarded
               text from any lexing code that runs later, as if the text had never appeared.

               This is not the normal way to consume lexed text.  For that, use "lex_read_to".

                       void    lex_unstuff(char *ptr)

       parse_arithexpr
               NOTE: this function is experimental and may change or be removed without notice.

               Parse a Perl arithmetic expression.  This may contain operators of precedence down
               to the bit shift operators.  The expression must be followed (and thus terminated)
               either by a comparison or lower-precedence operator or by something that would
               normally terminate an expression such as semicolon.  If "flags" has the
               "PARSE_OPTIONAL" bit set, then the expression is optional, otherwise it is
               mandatory.  It is up to the caller to ensure that the dynamic parser state
               ("PL_parser" et al) is correctly set to reflect the source of the code to be
               parsed and the lexical context for the expression.

               The op tree representing the expression is returned.  If an optional expression is
               absent, a null pointer is returned, otherwise the pointer will be non-null.

               If an error occurs in parsing or compilation, in most cases a valid op tree is
               returned anyway.  The error is reflected in the parser state, normally resulting
               in a single exception at the top level of parsing which covers all the compilation
               errors that occurred.  Some compilation errors, however, will throw an exception
               immediately.

                       OP *    parse_arithexpr(U32 flags)

       parse_barestmt
               NOTE: this function is experimental and may change or be removed without notice.

               Parse a single unadorned Perl statement.  This may be a normal imperative
               statement or a declaration that has compile-time effect.  It does not include any
               label or other affixture.  It is up to the caller to ensure that the dynamic
               parser state ("PL_parser" et al) is correctly set to reflect the source of the
               code to be parsed and the lexical context for the statement.

               The op tree representing the statement is returned.  This may be a null pointer if
               the statement is null, for example if it was actually a subroutine definition
               (which has compile-time side effects).  If not null, it will be ops directly
               implementing the statement, suitable to pass to "newSTATEOP".  It will not
               normally include a "nextstate" or equivalent op (except for those embedded in a
               scope contained entirely within the statement).

               If an error occurs in parsing or compilation, in most cases a valid op tree (most
               likely null) is returned anyway.  The error is reflected in the parser state,
               normally resulting in a single exception at the top level of parsing which covers
               all the compilation errors that occurred.  Some compilation errors, however, will
               throw an exception immediately.

               The "flags" parameter is reserved for future use, and must always be zero.

                       OP *    parse_barestmt(U32 flags)

       parse_block
               NOTE: this function is experimental and may change or be removed without notice.

               Parse a single complete Perl code block.  This consists of an opening brace, a
               sequence of statements, and a closing brace.  The block constitutes a lexical
               scope, so "my" variables and various compile-time effects can be contained within
               it.  It is up to the caller to ensure that the dynamic parser state ("PL_parser"
               et al) is correctly set to reflect the source of the code to be parsed and the
               lexical context for the statement.

               The op tree representing the code block is returned.  This is always a real op,
               never a null pointer.  It will normally be a "lineseq" list, including "nextstate"
               or equivalent ops.  No ops to construct any kind of runtime scope are included by
               virtue of it being a block.

               If an error occurs in parsing or compilation, in most cases a valid op tree (most
               likely null) is returned anyway.  The error is reflected in the parser state,
               normally resulting in a single exception at the top level of parsing which covers
               all the compilation errors that occurred.  Some compilation errors, however, will
               throw an exception immediately.

               The "flags" parameter is reserved for future use, and must always be zero.

                       OP *    parse_block(U32 flags)

       parse_fullexpr
               NOTE: this function is experimental and may change or be removed without notice.

               Parse a single complete Perl expression.  This allows the full expression grammar,
               including the lowest-precedence operators such as "or".  The expression must be
               followed (and thus terminated) by a token that an expression would normally be
               terminated by: end-of-file, closing bracketing punctuation, semicolon, or one of
               the keywords that signals a postfix expression-statement modifier.  If "flags" has
               the "PARSE_OPTIONAL" bit set, then the expression is optional, otherwise it is
               mandatory.  It is up to the caller to ensure that the dynamic parser state
               ("PL_parser" et al) is correctly set to reflect the source of the code to be
               parsed and the lexical context for the expression.

               The op tree representing the expression is returned.  If an optional expression is
               absent, a null pointer is returned, otherwise the pointer will be non-null.

               If an error occurs in parsing or compilation, in most cases a valid op tree is
               returned anyway.  The error is reflected in the parser state, normally resulting
               in a single exception at the top level of parsing which covers all the compilation
               errors that occurred.  Some compilation errors, however, will throw an exception
               immediately.

                       OP *    parse_fullexpr(U32 flags)

       parse_fullstmt
               NOTE: this function is experimental and may change or be removed without notice.

               Parse a single complete Perl statement.  This may be a normal imperative statement
               or a declaration that has compile-time effect, and may include optional labels.
               It is up to the caller to ensure that the dynamic parser state ("PL_parser" et al)
               is correctly set to reflect the source of the code to be parsed and the lexical
               context for the statement.

               The op tree representing the statement is returned.  This may be a null pointer if
               the statement is null, for example if it was actually a subroutine definition
               (which has compile-time side effects).  If not null, it will be the result of a
               "newSTATEOP" call, normally including a "nextstate" or equivalent op.

               If an error occurs in parsing or compilation, in most cases a valid op tree (most
               likely null) is returned anyway.  The error is reflected in the parser state,
               normally resulting in a single exception at the top level of parsing which covers
               all the compilation errors that occurred.  Some compilation errors, however, will
               throw an exception immediately.

               The "flags" parameter is reserved for future use, and must always be zero.

                       OP *    parse_fullstmt(U32 flags)

       parse_label
               NOTE: this function is experimental and may change or be removed without notice.

               Parse a single label, possibly optional, of the type that may prefix a Perl
               statement.  It is up to the caller to ensure that the dynamic parser state
               ("PL_parser" et al) is correctly set to reflect the source of the code to be
               parsed.  If "flags" has the "PARSE_OPTIONAL" bit set, then the label is optional,
               otherwise it is mandatory.

               The name of the label is returned in the form of a fresh scalar.  If an optional
               label is absent, a null pointer is returned.

               If an error occurs in parsing, which can only occur if the label is mandatory, a
               valid label is returned anyway.  The error is reflected in the parser state,
               normally resulting in a single exception at the top level of parsing which covers
               all the compilation errors that occurred.

                       SV *    parse_label(U32 flags)

       parse_listexpr
               NOTE: this function is experimental and may change or be removed without notice.

               Parse a Perl list expression.  This may contain operators of precedence down to
               the comma operator.  The expression must be followed (and thus terminated) either
               by a low-precedence logic operator such as "or" or by something that would
               normally terminate an expression such as semicolon.  If "flags" has the
               "PARSE_OPTIONAL" bit set, then the expression is optional, otherwise it is
               mandatory.  It is up to the caller to ensure that the dynamic parser state
               ("PL_parser" et al) is correctly set to reflect the source of the code to be
               parsed and the lexical context for the expression.

               The op tree representing the expression is returned.  If an optional expression is
               absent, a null pointer is returned, otherwise the pointer will be non-null.

               If an error occurs in parsing or compilation, in most cases a valid op tree is
               returned anyway.  The error is reflected in the parser state, normally resulting
               in a single exception at the top level of parsing which covers all the compilation
               errors that occurred.  Some compilation errors, however, will throw an exception
               immediately.

                       OP *    parse_listexpr(U32 flags)

       parse_stmtseq
               NOTE: this function is experimental and may change or be removed without notice.

               Parse a sequence of zero or more Perl statements.  These may be normal imperative
               statements, including optional labels, or declarations that have compile-time
               effect, or any mixture thereof.  The statement sequence ends when a closing brace
               or end-of-file is encountered in a place where a new statement could have validly
               started.  It is up to the caller to ensure that the dynamic parser state
               ("PL_parser" et al) is correctly set to reflect the source of the code to be
               parsed and the lexical context for the statements.

               The op tree representing the statement sequence is returned.  This may be a null
               pointer if the statements were all null, for example if there were no statements
               or if there were only subroutine definitions (which have compile-time side
               effects).  If not null, it will be a "lineseq" list, normally including
               "nextstate" or equivalent ops.

               If an error occurs in parsing or compilation, in most cases a valid op tree is
               returned anyway.  The error is reflected in the parser state, normally resulting
               in a single exception at the top level of parsing which covers all the compilation
               errors that occurred.  Some compilation errors, however, will throw an exception
               immediately.

               The "flags" parameter is reserved for future use, and must always be zero.

                       OP *    parse_stmtseq(U32 flags)

       parse_termexpr
               NOTE: this function is experimental and may change or be removed without notice.

               Parse a Perl term expression.  This may contain operators of precedence down to
               the assignment operators.  The expression must be followed (and thus terminated)
               either by a comma or lower-precedence operator or by something that would normally
               terminate an expression such as semicolon.  If "flags" has the "PARSE_OPTIONAL"
               bit set, then the expression is optional, otherwise it is mandatory.  It is up to
               the caller to ensure that the dynamic parser state ("PL_parser" et al) is
               correctly set to reflect the source of the code to be parsed and the lexical
               context for the expression.

               The op tree representing the expression is returned.  If an optional expression is
               absent, a null pointer is returned, otherwise the pointer will be non-null.

               If an error occurs in parsing or compilation, in most cases a valid op tree is
               returned anyway.  The error is reflected in the parser state, normally resulting
               in a single exception at the top level of parsing which covers all the compilation
               errors that occurred.  Some compilation errors, however, will throw an exception
               immediately.

                       OP *    parse_termexpr(U32 flags)

       PL_parser
               Pointer to a structure encapsulating the state of the parsing operation currently
               in progress.  The pointer can be locally changed to perform a nested parse without
               interfering with the state of an outer parse.  Individual members of "PL_parser"
               have their own documentation.

       PL_parser->bufend
               NOTE: this function is experimental and may change or be removed without notice.

               Direct pointer to the end of the chunk of text currently being lexed, the end of
               the lexer buffer.  This is equal to "SvPVX(PL_parser->linestr) +
               SvCUR(PL_parser->linestr)".  A "NUL" character (zero octet) is always located at
               the end of the buffer, and does not count as part of the buffer's contents.

       PL_parser->bufptr
               NOTE: this function is experimental and may change or be removed without notice.

               Points to the current position of lexing inside the lexer buffer.  Characters
               around this point may be freely examined, within the range delimited by
               "SvPVX("PL_parser->linestr")" and "PL_parser->bufend".  The octets of the buffer
               may be intended to be interpreted as either UTF-8 or Latin-1, as indicated by
               "lex_bufutf8".

               Lexing code (whether in the Perl core or not) moves this pointer past the
               characters that it consumes.  It is also expected to perform some bookkeeping
               whenever a newline character is consumed.  This movement can be more conveniently
               performed by the function "lex_read_to", which handles newlines appropriately.

               Interpretation of the buffer's octets can be abstracted out by using the slightly
               higher-level functions "lex_peek_unichar" and "lex_read_unichar".

       PL_parser->linestart
               NOTE: this function is experimental and may change or be removed without notice.

               Points to the start of the current line inside the lexer buffer.  This is useful
               for indicating at which column an error occurred, and not much else.  This must be
               updated by any lexing code that consumes a newline; the function "lex_read_to"
               handles this detail.

       PL_parser->linestr
               NOTE: this function is experimental and may change or be removed without notice.

               Buffer scalar containing the chunk currently under consideration of the text
               currently being lexed.  This is always a plain string scalar (for which "SvPOK" is
               true).  It is not intended to be used as a scalar by normal scalar means; instead
               refer to the buffer directly by the pointer variables described below.

               The lexer maintains various "char*" pointers to things in the "PL_parser->linestr"
               buffer.  If "PL_parser->linestr" is ever reallocated, all of these pointers must
               be updated.  Don't attempt to do this manually, but rather use "lex_grow_linestr"
               if you need to reallocate the buffer.

               The content of the text chunk in the buffer is commonly exactly one complete line
               of input, up to and including a newline terminator, but there are situations where
               it is otherwise.  The octets of the buffer may be intended to be interpreted as
               either UTF-8 or Latin-1.  The function "lex_bufutf8" tells you which.  Do not use
               the "SvUTF8" flag on this scalar, which may disagree with it.

               For direct examination of the buffer, the variable "PL_parser->bufend" points to
               the end of the buffer.  The current lexing position is pointed to by
               "PL_parser->bufptr".  Direct use of these pointers is usually preferable to
               examination of the scalar through normal scalar means.

Locale-related functions and macros

       DECLARATION_FOR_LC_NUMERIC_MANIPULATION
               This macro should be used as a statement.  It declares a private variable (whose
               name begins with an underscore) that is needed by the other macros in this
               section.  Failing to include this correctly should lead to a syntax error.  For
               compatibility with C89 C compilers it should be placed in a block before any
               executable statements.

                       void    DECLARATION_FOR_LC_NUMERIC_MANIPULATION

       RESTORE_LC_NUMERIC
               This is used in conjunction with one of the macros
               "STORE_LC_NUMERIC_SET_TO_NEEDED" and "STORE_LC_NUMERIC_FORCE_TO_UNDERLYING"

               to properly restore the "LC_NUMERIC" state.

               A call to "DECLARATION_FOR_LC_NUMERIC_MANIPULATION" must have been made to declare
               at compile time a private variable used by this macro and the two "STORE" ones.
               This macro should be called as a single statement, not an expression, but with an
               empty argument list, like this:

                {
                   DECLARATION_FOR_LC_NUMERIC_MANIPULATION;
                    ...
                   RESTORE_LC_NUMERIC();
                    ...
                }

                       void    RESTORE_LC_NUMERIC()

       STORE_LC_NUMERIC_FORCE_TO_UNDERLYING
               This is used by XS code that that is "LC_NUMERIC" locale-aware to force the locale
               for category "LC_NUMERIC" to be what perl thinks is the current underlying locale.
               (The perl interpreter could be wrong about what the underlying locale actually is
               if some C or XS code has called the C library function setlocale(3) behind its
               back; calling "sync_locale" before calling this macro will update perl's records.)

               A call to "DECLARATION_FOR_LC_NUMERIC_MANIPULATION" must have been made to declare
               at compile time a private variable used by this macro.  This macro should be
               called as a single statement, not an expression, but with an empty argument list,
               like this:

                {
                   DECLARATION_FOR_LC_NUMERIC_MANIPULATION;
                    ...
                   STORE_LC_NUMERIC_FORCE_TO_UNDERLYING();
                    ...
                   RESTORE_LC_NUMERIC();
                    ...
                }

               The private variable is used to save the current locale state, so that the
               requisite matching call to "RESTORE_LC_NUMERIC" can restore it.

                       void    STORE_LC_NUMERIC_FORCE_TO_UNDERLYING()

       STORE_LC_NUMERIC_SET_TO_NEEDED
               This is used to help wrap XS or C code that that is "LC_NUMERIC" locale-aware.
               This locale category is generally kept set to the C locale by Perl for backwards
               compatibility, and because most XS code that reads floating point values can cope
               only with the decimal radix character being a dot.

               This macro makes sure the current "LC_NUMERIC" state is set properly, to be aware
               of locale if the call to the XS or C code from the Perl program is from within the
               scope of a "use locale"; or to ignore locale if the call is instead from outside
               such scope.

               This macro is the start of wrapping the C or XS code; the wrap ending is done by
               calling the "RESTORE_LC_NUMERIC" macro after the operation.  Otherwise the state
               can be changed that will adversely affect other XS code.

               A call to "DECLARATION_FOR_LC_NUMERIC_MANIPULATION" must have been made to declare
               at compile time a private variable used by this macro.  This macro should be
               called as a single statement, not an expression, but with an empty argument list,
               like this:

                {
                   DECLARATION_FOR_LC_NUMERIC_MANIPULATION;
                    ...
                   STORE_LC_NUMERIC_SET_TO_NEEDED();
                    ...
                   RESTORE_LC_NUMERIC();
                    ...
                }

                       void    STORE_LC_NUMERIC_SET_TO_NEEDED()

       sync_locale
               Changing the program's locale should be avoided by XS code.  Nevertheless, certain
               non-Perl libraries called from XS, such as "Gtk" do so.  When this happens, Perl
               needs to be told that the locale has changed.  Use this function to do so, before
               returning to Perl.

                       void    sync_locale()

Magical Functions

       mg_clear
               Clear something magical that the SV represents.  See "sv_magic".

                       int     mg_clear(SV* sv)

       mg_copy Copies the magic from one SV to another.  See "sv_magic".

                       int     mg_copy(SV *sv, SV *nsv, const char *key,
                                       I32 klen)

       mg_find Finds the magic pointer for "type" matching the SV.  See "sv_magic".

                       MAGIC*  mg_find(const SV* sv, int type)

       mg_findext
               Finds the magic pointer of "type" with the given "vtbl" for the "SV".  See
               "sv_magicext".

                       MAGIC*  mg_findext(const SV* sv, int type,
                                          const MGVTBL *vtbl)

       mg_free Free any magic storage used by the SV.  See "sv_magic".

                       int     mg_free(SV* sv)

       mg_free_type
               Remove any magic of type "how" from the SV "sv".  See "sv_magic".

                       void    mg_free_type(SV *sv, int how)

       mg_get  Do magic before a value is retrieved from the SV.  The type of SV must be >=
               "SVt_PVMG".  See "sv_magic".

                       int     mg_get(SV* sv)

       mg_length
               DEPRECATED!  It is planned to remove this function from a future release of Perl.
               Do not use it for new code; remove it from existing code.

               Reports on the SV's length in bytes, calling length magic if available, but does
               not set the UTF8 flag on "sv".  It will fall back to 'get' magic if there is no
               'length' magic, but with no indication as to whether it called 'get' magic.  It
               assumes "sv" is a "PVMG" or higher.  Use "sv_len()" instead.

                       U32     mg_length(SV* sv)

       mg_magical
               Turns on the magical status of an SV.  See "sv_magic".

                       void    mg_magical(SV* sv)

       mg_set  Do magic after a value is assigned to the SV.  See "sv_magic".

                       int     mg_set(SV* sv)

       SvGETMAGIC
               Invokes "mg_get" on an SV if it has 'get' magic.  For example, this will call
               "FETCH" on a tied variable.  This macro evaluates its argument more than once.

                       void    SvGETMAGIC(SV* sv)

       SvLOCK  Arranges for a mutual exclusion lock to be obtained on "sv" if a suitable module
               has been loaded.

                       void    SvLOCK(SV* sv)

       SvSETMAGIC
               Invokes "mg_set" on an SV if it has 'set' magic.  This is necessary after
               modifying a scalar, in case it is a magical variable like $| or a tied variable
               (it calls "STORE").  This macro evaluates its argument more than once.

                       void    SvSETMAGIC(SV* sv)

       SvSetMagicSV
               Like "SvSetSV", but does any set magic required afterwards.

                       void    SvSetMagicSV(SV* dsv, SV* ssv)

       SvSetMagicSV_nosteal
               Like "SvSetSV_nosteal", but does any set magic required afterwards.

                       void    SvSetMagicSV_nosteal(SV* dsv, SV* ssv)

       SvSetSV Calls "sv_setsv" if "dsv" is not the same as "ssv".  May evaluate arguments more
               than once.  Does not handle 'set' magic on the destination SV.

                       void    SvSetSV(SV* dsv, SV* ssv)

       SvSetSV_nosteal
               Calls a non-destructive version of "sv_setsv" if "dsv" is not the same as "ssv".
               May evaluate arguments more than once.

                       void    SvSetSV_nosteal(SV* dsv, SV* ssv)

       SvSHARE Arranges for "sv" to be shared between threads if a suitable module has been
               loaded.

                       void    SvSHARE(SV* sv)

       SvUNLOCK
               Releases a mutual exclusion lock on "sv" if a suitable module has been loaded.

                       void    SvUNLOCK(SV* sv)

Memory Management

       Copy    The XSUB-writer's interface to the C "memcpy" function.  The "src" is the source,
               "dest" is the destination, "nitems" is the number of items, and "type" is the
               type.  May fail on overlapping copies.  See also "Move".

                       void    Copy(void* src, void* dest, int nitems, type)

       CopyD   Like "Copy" but returns "dest".  Useful for encouraging compilers to tail-call
               optimise.

                       void *  CopyD(void* src, void* dest, int nitems, type)

       Move    The XSUB-writer's interface to the C "memmove" function.  The "src" is the source,
               "dest" is the destination, "nitems" is the number of items, and "type" is the
               type.  Can do overlapping moves.  See also "Copy".

                       void    Move(void* src, void* dest, int nitems, type)

       MoveD   Like "Move" but returns "dest".  Useful for encouraging compilers to tail-call
               optimise.

                       void *  MoveD(void* src, void* dest, int nitems, type)

       Newx    The XSUB-writer's interface to the C "malloc" function.

               Memory obtained by this should ONLY be freed with "Safefree".

               In 5.9.3, Newx() and friends replace the older New() API, and drops the first
               parameter, x, a debug aid which allowed callers to identify themselves.  This aid
               has been superseded by a new build option, PERL_MEM_LOG (see "PERL_MEM_LOG" in
               perlhacktips).  The older API is still there for use in XS modules supporting
               older perls.

                       void    Newx(void* ptr, int nitems, type)

       Newxc   The XSUB-writer's interface to the C "malloc" function, with cast.  See also
               "Newx".

               Memory obtained by this should ONLY be freed with "Safefree".

                       void    Newxc(void* ptr, int nitems, type, cast)

       Newxz   The XSUB-writer's interface to the C "malloc" function.  The allocated memory is
               zeroed with "memzero".  See also "Newx".

               Memory obtained by this should ONLY be freed with "Safefree".

                       void    Newxz(void* ptr, int nitems, type)

       Poison  PoisonWith(0xEF) for catching access to freed memory.

                       void    Poison(void* dest, int nitems, type)

       PoisonFree
               PoisonWith(0xEF) for catching access to freed memory.

                       void    PoisonFree(void* dest, int nitems, type)

       PoisonNew
               PoisonWith(0xAB) for catching access to allocated but uninitialized memory.

                       void    PoisonNew(void* dest, int nitems, type)

       PoisonWith
               Fill up memory with a byte pattern (a byte repeated over and over again) that
               hopefully catches attempts to access uninitialized memory.

                       void    PoisonWith(void* dest, int nitems, type,
                                          U8 byte)

       Renew   The XSUB-writer's interface to the C "realloc" function.

               Memory obtained by this should ONLY be freed with "Safefree".

                       void    Renew(void* ptr, int nitems, type)

       Renewc  The XSUB-writer's interface to the C "realloc" function, with cast.

               Memory obtained by this should ONLY be freed with "Safefree".

                       void    Renewc(void* ptr, int nitems, type, cast)

       Safefree
               The XSUB-writer's interface to the C "free" function.

               This should ONLY be used on memory obtained using "Newx" and friends.

                       void    Safefree(void* ptr)

       savepv  Perl's version of "strdup()".  Returns a pointer to a newly allocated string which
               is a duplicate of "pv".  The size of the string is determined by "strlen()", which
               means it may not contain embedded "NUL" characters and must have a trailing "NUL".
               The memory allocated for the new string can be freed with the "Safefree()"
               function.

               On some platforms, Windows for example, all allocated memory owned by a thread is
               deallocated when that thread ends.  So if you need that not to happen, you need to
               use the shared memory functions, such as "savesharedpv".

                       char*   savepv(const char* pv)

       savepvn Perl's version of what "strndup()" would be if it existed.  Returns a pointer to a
               newly allocated string which is a duplicate of the first "len" bytes from "pv",
               plus a trailing "NUL" byte.  The memory allocated for the new string can be freed
               with the "Safefree()" function.

               On some platforms, Windows for example, all allocated memory owned by a thread is
               deallocated when that thread ends.  So if you need that not to happen, you need to
               use the shared memory functions, such as "savesharedpvn".

                       char*   savepvn(const char* pv, I32 len)

       savepvs Like "savepvn", but takes a "NUL"-terminated literal string instead of a
               string/length pair.

                       char*   savepvs(const char* s)

       savesharedpv
               A version of "savepv()" which allocates the duplicate string in memory which is
               shared between threads.

                       char*   savesharedpv(const char* pv)

       savesharedpvn
               A version of "savepvn()" which allocates the duplicate string in memory which is
               shared between threads.  (With the specific difference that a "NULL" pointer is
               not acceptable)

                       char*   savesharedpvn(const char *const pv,
                                             const STRLEN len)

       savesharedpvs
               A version of "savepvs()" which allocates the duplicate string in memory which is
               shared between threads.

                       char*   savesharedpvs(const char* s)

       savesharedsvpv
               A version of "savesharedpv()" which allocates the duplicate string in memory which
               is shared between threads.

                       char*   savesharedsvpv(SV *sv)

       savesvpv
               A version of "savepv()"/"savepvn()" which gets the string to duplicate from the
               passed in SV using "SvPV()"

               On some platforms, Windows for example, all allocated memory owned by a thread is
               deallocated when that thread ends.  So if you need that not to happen, you need to
               use the shared memory functions, such as "savesharedsvpv".

                       char*   savesvpv(SV* sv)

       StructCopy
               This is an architecture-independent macro to copy one structure to another.

                       void    StructCopy(type *src, type *dest, type)

       Zero    The XSUB-writer's interface to the C "memzero" function.  The "dest" is the
               destination, "nitems" is the number of items, and "type" is the type.

                       void    Zero(void* dest, int nitems, type)

       ZeroD   Like "Zero" but returns dest.  Useful for encouraging compilers to tail-call
               optimise.

                       void *  ZeroD(void* dest, int nitems, type)

Miscellaneous Functions

       dump_c_backtrace
               Dumps the C backtrace to the given "fp".

               Returns true if a backtrace could be retrieved, false if not.

                       bool    dump_c_backtrace(PerlIO* fp, int max_depth,
                                                int skip)

       fbm_compile
               Analyses the string in order to make fast searches on it using "fbm_instr()" --
               the Boyer-Moore algorithm.

                       void    fbm_compile(SV* sv, U32 flags)

       fbm_instr
               Returns the location of the SV in the string delimited by "big" and "bigend"
               ("bigend") is the char following the last char).  It returns "NULL" if the string
               can't be found.  The "sv" does not have to be "fbm_compiled", but the search will
               not be as fast then.

                       char*   fbm_instr(unsigned char* big,
                                         unsigned char* bigend, SV* littlestr,
                                         U32 flags)

       foldEQ  Returns true if the leading "len" bytes of the strings "s1" and "s2" are the same
               case-insensitively; false otherwise.  Uppercase and lowercase ASCII range bytes
               match themselves and their opposite case counterparts.  Non-cased and non-ASCII
               range bytes match only themselves.

                       I32     foldEQ(const char* a, const char* b, I32 len)

       foldEQ_locale
               Returns true if the leading "len" bytes of the strings "s1" and "s2" are the same
               case-insensitively in the current locale; false otherwise.

                       I32     foldEQ_locale(const char* a, const char* b,
                                             I32 len)

       form    Takes a sprintf-style format pattern and conventional (non-SV) arguments and
               returns the formatted string.

                   (char *) Perl_form(pTHX_ const char* pat, ...)

               can be used any place a string (char *) is required:

                   char * s = Perl_form("%d.%d",major,minor);

               Uses a single private buffer so if you want to format several strings you must
               explicitly copy the earlier strings away (and free the copies when you are done).

                       char*   form(const char* pat, ...)

       getcwd_sv
               Fill "sv" with current working directory

                       int     getcwd_sv(SV* sv)

       get_c_backtrace_dump
               Returns a SV containing a dump of "depth" frames of the call stack, skipping the
               "skip" innermost ones.  "depth" of 20 is usually enough.

               The appended output looks like:

               ...  1   10e004812:0082   Perl_croak   util.c:1716    /usr/bin/perl 2
               10df8d6d2:1d72   perl_parse   perl.c:3975    /usr/bin/perl ...

               The fields are tab-separated.  The first column is the depth (zero being the
               innermost non-skipped frame).  In the hex:offset, the hex is where the program
               counter was in "S_parse_body", and the :offset (might be missing) tells how much
               inside the "S_parse_body" the program counter was.

               The "util.c:1716" is the source code file and line number.

               The /usr/bin/perl is obvious (hopefully).

               Unknowns are "-".  Unknowns can happen unfortunately quite easily: if the platform
               doesn't support retrieving the information; if the binary is missing the debug
               information; if the optimizer has transformed the code by for example inlining.

                       SV*     get_c_backtrace_dump(int max_depth, int skip)

       ibcmp   This is a synonym for "(! foldEQ())"

                       I32     ibcmp(const char* a, const char* b, I32 len)

       ibcmp_locale
               This is a synonym for "(! foldEQ_locale())"

                       I32     ibcmp_locale(const char* a, const char* b,
                                            I32 len)

       is_safe_syscall
               Test that the given "pv" doesn't contain any internal "NUL" characters.  If it
               does, set "errno" to "ENOENT", optionally warn, and return FALSE.

               Return TRUE if the name is safe.

               Used by the "IS_SAFE_SYSCALL()" macro.

                       bool    is_safe_syscall(const char *pv, STRLEN len,
                                               const char *what,
                                               const char *op_name)

       memEQ   Test two buffers (which may contain embedded "NUL" characters, to see if they are
               equal.  The "len" parameter indicates the number of bytes to compare.  Returns
               zero if equal, or non-zero if non-equal.

                       bool    memEQ(char* s1, char* s2, STRLEN len)

       memNE   Test two buffers (which may contain embedded "NUL" characters, to see if they are
               not equal.  The "len" parameter indicates the number of bytes to compare.  Returns
               zero if non-equal, or non-zero if equal.

                       bool    memNE(char* s1, char* s2, STRLEN len)

       mess    Take a sprintf-style format pattern and argument list.  These are used to generate
               a string message.  If the message does not end with a newline, then it will be
               extended with some indication of the current location in the code, as described
               for "mess_sv".

               Normally, the resulting message is returned in a new mortal SV.  During global
               destruction a single SV may be shared between uses of this function.

                       SV *    mess(const char *pat, ...)

       mess_sv Expands a message, intended for the user, to include an indication of the current
               location in the code, if the message does not already appear to be complete.

               "basemsg" is the initial message or object.  If it is a reference, it will be used
               as-is and will be the result of this function.  Otherwise it is used as a string,
               and if it already ends with a newline, it is taken to be complete, and the result
               of this function will be the same string.  If the message does not end with a
               newline, then a segment such as "at foo.pl line 37" will be appended, and possibly
               other clauses indicating the current state of execution.  The resulting message
               will end with a dot and a newline.

               Normally, the resulting message is returned in a new mortal SV.  During global
               destruction a single SV may be shared between uses of this function.  If "consume"
               is true, then the function is permitted (but not required) to modify and return
               "basemsg" instead of allocating a new SV.

                       SV *    mess_sv(SV *basemsg, bool consume)

       my_snprintf
               The C library "snprintf" functionality, if available and standards-compliant (uses
               "vsnprintf", actually).  However, if the "vsnprintf" is not available, will
               unfortunately use the unsafe "vsprintf" which can overrun the buffer (there is an
               overrun check, but that may be too late).  Consider using "sv_vcatpvf" instead, or
               getting "vsnprintf".

                       int     my_snprintf(char *buffer, const Size_t len,
                                           const char *format, ...)

       my_sprintf
               The C library "sprintf", wrapped if necessary, to ensure that it will return the
               length of the string written to the buffer.  Only rare pre-ANSI systems need the
               wrapper function - usually this is a direct call to "sprintf".

                       int     my_sprintf(char *buffer, const char *pat, ...)

       my_strlcat
               The C library "strlcat" if available, or a Perl implementation of it.  This
               operates on C "NUL"-terminated strings.

               "my_strlcat()" appends string "src" to the end of "dst".  It will append at most
               "size - strlen(dst) - 1" characters.  It will then "NUL"-terminate, unless "size"
               is 0 or the original "dst" string was longer than "size" (in practice this should
               not happen as it means that either "size" is incorrect or that "dst" is not a
               proper "NUL"-terminated string).

               Note that "size" is the full size of the destination buffer and the result is
               guaranteed to be "NUL"-terminated if there is room.  Note that room for the "NUL"
               should be included in "size".

               The return value is the total length that "dst" would have if "size" is
               sufficiently large.  Thus it is the initial length of "dst" plus the length of
               "src".  If "size" is smaller than the return, the excess was not appended.

                       Size_t  my_strlcat(char *dst, const char *src,
                                          Size_t size)

       my_strlcpy
               The C library "strlcpy" if available, or a Perl implementation of it.  This
               operates on C "NUL"-terminated strings.

               "my_strlcpy()" copies up to "size - 1" characters from the string "src" to "dst",
               "NUL"-terminating the result if "size" is not 0.

               The return value is the total length "src" would be if the copy completely
               succeeded.  If it is larger than "size", the excess was not copied.

                       Size_t  my_strlcpy(char *dst, const char *src,
                                          Size_t size)

       my_vsnprintf
               The C library "vsnprintf" if available and standards-compliant.  However, if if
               the "vsnprintf" is not available, will unfortunately use the unsafe "vsprintf"
               which can overrun the buffer (there is an overrun check, but that may be too
               late).  Consider using "sv_vcatpvf" instead, or getting "vsnprintf".

                       int     my_vsnprintf(char *buffer, const Size_t len,
                                            const char *format, va_list ap)

       ninstr  Find the first (leftmost) occurrence of a sequence of bytes within another
               sequence.  This is the Perl version of "strstr()", extended to handle arbitrary
               sequences, potentially containing embedded "NUL" characters ("NUL" is what the
               initial "n" in the function name stands for; some systems have an equivalent,
               "memmem()", but with a somewhat different API).

               Another way of thinking about this function is finding a needle in a haystack.
               "big" points to the first byte in the haystack.  "big_end" points to one byte
               beyond the final byte in the haystack.  "little" points to the first byte in the
               needle.  "little_end" points to one byte beyond the final byte in the needle.  All
               the parameters must be non-"NULL".

               The function returns "NULL" if there is no occurrence of "little" within "big".
               If "little" is the empty string, "big" is returned.

               Because this function operates at the byte level, and because of the inherent
               characteristics of UTF-8 (or UTF-EBCDIC), it will work properly if both the needle
               and the haystack are strings with the same UTF-8ness, but not if the UTF-8ness
               differs.

                       char *  ninstr(char * big, char * bigend, char * little,
                                      char * little_end)

       PERL_SYS_INIT
               Provides system-specific tune up of the C runtime environment necessary to run
               Perl interpreters.  This should be called only once, before creating any Perl
               interpreters.

                       void    PERL_SYS_INIT(int *argc, char*** argv)

       PERL_SYS_INIT3
               Provides system-specific tune up of the C runtime environment necessary to run
               Perl interpreters.  This should be called only once, before creating any Perl
               interpreters.

                       void    PERL_SYS_INIT3(int *argc, char*** argv,
                                              char*** env)

       PERL_SYS_TERM
               Provides system-specific clean up of the C runtime environment after running Perl
               interpreters.  This should be called only once, after freeing any remaining Perl
               interpreters.

                       void    PERL_SYS_TERM()

       quadmath_format_needed
               "quadmath_format_needed()" returns true if the "format" string seems to contain at
               least one non-Q-prefixed "%[efgaEFGA]" format specifier, or returns false
               otherwise.

               The format specifier detection is not complete printf-syntax detection, but it
               should catch most common cases.

               If true is returned, those arguments should in theory be processed with
               "quadmath_snprintf()", but in case there is more than one such format specifier
               (see "quadmath_format_single"), and if there is anything else beyond that one
               (even just a single byte), they cannot be processed because "quadmath_snprintf()"
               is very strict, accepting only one format spec, and nothing else.  In this case,
               the code should probably fail.

                       bool    quadmath_format_needed(const char* format)

       quadmath_format_single
               "quadmath_snprintf()" is very strict about its "format" string and will fail,
               returning -1, if the format is invalid.  It accepts exactly one format spec.

               "quadmath_format_single()" checks that the intended single spec looks sane: begins
               with "%", has only one "%", ends with "[efgaEFGA]", and has "Q" before it.  This
               is not a full "printf syntax check", just the basics.

               Returns the format if it is valid, NULL if not.

               "quadmath_format_single()" can and will actually patch in the missing "Q", if
               necessary.  In this case it will return the modified copy of the format, which the
               caller will need to free.

               See also "quadmath_format_needed".

                       const char* quadmath_format_single(const char* format)

       READ_XDIGIT
               Returns the value of an ASCII-range hex digit and advances the string pointer.
               Behaviour is only well defined when isXDIGIT(*str) is true.

                       U8      READ_XDIGIT(char str*)

       rninstr Like "ninstr", but instead finds the final (rightmost) occurrence of a sequence of
               bytes within another sequence, returning "NULL" if there is no such occurrence.

                       char *  rninstr(char * big, char * bigend,
                                       char * little, char * little_end)

       strEQ   Test two "NUL"-terminated strings to see if they are equal.  Returns true or
               false.

                       bool    strEQ(char* s1, char* s2)

       strGE   Test two "NUL"-terminated strings to see if the first, "s1", is greater than or
               equal to the second, "s2".  Returns true or false.

                       bool    strGE(char* s1, char* s2)

       strGT   Test two "NUL"-terminated strings to see if the first, "s1", is greater than the
               second, "s2".  Returns true or false.

                       bool    strGT(char* s1, char* s2)

       strLE   Test two "NUL"-terminated strings to see if the first, "s1", is less than or equal
               to the second, "s2".  Returns true or false.

                       bool    strLE(char* s1, char* s2)

       strLT   Test two "NUL"-terminated strings to see if the first, "s1", is less than the
               second, "s2".  Returns true or false.

                       bool    strLT(char* s1, char* s2)

       strNE   Test two "NUL"-terminated strings to see if they are different.  Returns true or
               false.

                       bool    strNE(char* s1, char* s2)

       strnEQ  Test two "NUL"-terminated strings to see if they are equal.  The "len" parameter
               indicates the number of bytes to compare.  Returns true or false.  (A wrapper for
               "strncmp").

                       bool    strnEQ(char* s1, char* s2, STRLEN len)

       strnNE  Test two "NUL"-terminated strings to see if they are different.  The "len"
               parameter indicates the number of bytes to compare.  Returns true or false.  (A
               wrapper for "strncmp").

                       bool    strnNE(char* s1, char* s2, STRLEN len)

       sv_destroyable
               Dummy routine which reports that object can be destroyed when there is no sharing
               module present.  It ignores its single SV argument, and returns 'true'.  Exists to
               avoid test for a "NULL" function pointer and because it could potentially warn
               under some level of strict-ness.

                       bool    sv_destroyable(SV *sv)

       sv_nosharing
               Dummy routine which "shares" an SV when there is no sharing module present.  Or
               "locks" it.  Or "unlocks" it.  In other words, ignores its single SV argument.
               Exists to avoid test for a "NULL" function pointer and because it could
               potentially warn under some level of strict-ness.

                       void    sv_nosharing(SV *sv)

       vmess   "pat" and "args" are a sprintf-style format pattern and encapsulated argument
               list, respectively.  These are used to generate a string message.  If the message
               does not end with a newline, then it will be extended with some indication of the
               current location in the code, as described for "mess_sv".

               Normally, the resulting message is returned in a new mortal SV.  During global
               destruction a single SV may be shared between uses of this function.

                       SV *    vmess(const char *pat, va_list *args)

MRO Functions

       These functions are related to the method resolution order of perl classes

       mro_get_linear_isa
               Returns the mro linearisation for the given stash.  By default, this will be
               whatever "mro_get_linear_isa_dfs" returns unless some other MRO is in effect for
               the stash.  The return value is a read-only AV*.

               You are responsible for "SvREFCNT_inc()" on the return value if you plan to store
               it anywhere semi-permanently (otherwise it might be deleted out from under you the
               next time the cache is invalidated).

                       AV*     mro_get_linear_isa(HV* stash)

       mro_method_changed_in
               Invalidates method caching on any child classes of the given stash, so that they
               might notice the changes in this one.

               Ideally, all instances of "PL_sub_generation++" in perl source outside of mro.c
               should be replaced by calls to this.

               Perl automatically handles most of the common ways a method might be redefined.
               However, there are a few ways you could change a method in a stash without the
               cache code noticing, in which case you need to call this method afterwards:

               1) Directly manipulating the stash HV entries from XS code.

               2) Assigning a reference to a readonly scalar constant into a stash entry in order
               to create a constant subroutine (like constant.pm does).

               This same method is available from pure perl via,
               "mro::method_changed_in(classname)".

                       void    mro_method_changed_in(HV* stash)

       mro_register
               Registers a custom mro plugin.  See perlmroapi for details.

                       void    mro_register(const struct mro_alg *mro)

Multicall Functions

       dMULTICALL
               Declare local variables for a multicall.  See "LIGHTWEIGHT CALLBACKS" in perlcall.

                               dMULTICALL;

       MULTICALL
               Make a lightweight callback.  See "LIGHTWEIGHT CALLBACKS" in perlcall.

                               MULTICALL;

       POP_MULTICALL
               Closing bracket for a lightweight callback.  See "LIGHTWEIGHT CALLBACKS" in
               perlcall.

                               POP_MULTICALL;

       PUSH_MULTICALL
               Opening bracket for a lightweight callback.  See "LIGHTWEIGHT CALLBACKS" in
               perlcall.

                               PUSH_MULTICALL;

Numeric functions

       grok_bin
               converts a string representing a binary number to numeric form.

               On entry "start" and *len give the string to scan, *flags gives conversion flags,
               and "result" should be "NULL" or a pointer to an NV.  The scan stops at the end of
               the string, or the first invalid character.  Unless "PERL_SCAN_SILENT_ILLDIGIT" is
               set in *flags, encountering an invalid character will also trigger a warning.  On
               return *len is set to the length of the scanned string, and *flags gives output
               flags.

               If the value is <= "UV_MAX" it is returned as a UV, the output flags are clear,
               and nothing is written to *result.  If the value is > "UV_MAX", "grok_bin" returns
               "UV_MAX", sets "PERL_SCAN_GREATER_THAN_UV_MAX" in the output flags, and writes the
               value to *result (or the value is discarded if "result" is NULL).

               The binary number may optionally be prefixed with "0b" or "b" unless
               "PERL_SCAN_DISALLOW_PREFIX" is set in *flags on entry.  If
               "PERL_SCAN_ALLOW_UNDERSCORES" is set in *flags then the binary number may use "_"
               characters to separate digits.

                       UV      grok_bin(const char* start, STRLEN* len_p,
                                        I32* flags, NV *result)

       grok_hex
               converts a string representing a hex number to numeric form.

               On entry "start" and *len_p give the string to scan, *flags gives conversion
               flags, and "result" should be "NULL" or a pointer to an NV.  The scan stops at the
               end of the string, or the first invalid character.  Unless
               "PERL_SCAN_SILENT_ILLDIGIT" is set in *flags, encountering an invalid character
               will also trigger a warning.  On return *len is set to the length of the scanned
               string, and *flags gives output flags.

               If the value is <= "UV_MAX" it is returned as a UV, the output flags are clear,
               and nothing is written to *result.  If the value is > "UV_MAX", "grok_hex" returns
               "UV_MAX", sets "PERL_SCAN_GREATER_THAN_UV_MAX" in the output flags, and writes the
               value to *result (or the value is discarded if "result" is "NULL").

               The hex number may optionally be prefixed with "0x" or "x" unless
               "PERL_SCAN_DISALLOW_PREFIX" is set in *flags on entry.  If
               "PERL_SCAN_ALLOW_UNDERSCORES" is set in *flags then the hex number may use "_"
               characters to separate digits.

                       UV      grok_hex(const char* start, STRLEN* len_p,
                                        I32* flags, NV *result)

       grok_infnan
               Helper for "grok_number()", accepts various ways of spelling "infinity" or "not a
               number", and returns one of the following flag combinations:

                 IS_NUMBER_INFINITE
                 IS_NUMBER_NAN
                 IS_NUMBER_INFINITE | IS_NUMBER_NEG
                 IS_NUMBER_NAN | IS_NUMBER_NEG
                 0

               possibly |-ed with "IS_NUMBER_TRAILING".

               If an infinity or a not-a-number is recognized, *sp will point to one byte past
               the end of the recognized string.  If the recognition fails, zero is returned, and
               *sp will not move.

                       int     grok_infnan(const char** sp, const char *send)

       grok_number
               Identical to "grok_number_flags()" with "flags" set to zero.

                       int     grok_number(const char *pv, STRLEN len,
                                           UV *valuep)

       grok_number_flags
               Recognise (or not) a number.  The type of the number is returned (0 if
               unrecognised), otherwise it is a bit-ORed combination of "IS_NUMBER_IN_UV",
               "IS_NUMBER_GREATER_THAN_UV_MAX", "IS_NUMBER_NOT_INT", "IS_NUMBER_NEG",
               "IS_NUMBER_INFINITY", "IS_NUMBER_NAN" (defined in perl.h).

               If the value of the number can fit in a UV, it is returned in *valuep.
               "IS_NUMBER_IN_UV" will be set to indicate that *valuep is valid, "IS_NUMBER_IN_UV"
               will never be set unless *valuep is valid, but *valuep may have been assigned to
               during processing even though "IS_NUMBER_IN_UV" is not set on return.  If "valuep"
               is "NULL", "IS_NUMBER_IN_UV" will be set for the same cases as when "valuep" is
               non-"NULL", but no actual assignment (or SEGV) will occur.

               "IS_NUMBER_NOT_INT" will be set with "IS_NUMBER_IN_UV" if trailing decimals were
               seen (in which case *valuep gives the true value truncated to an integer), and
               "IS_NUMBER_NEG" if the number is negative (in which case *valuep holds the
               absolute value).  "IS_NUMBER_IN_UV" is not set if e notation was used or the
               number is larger than a UV.

               "flags" allows only "PERL_SCAN_TRAILING", which allows for trailing non-numeric
               text on an otherwise successful grok, setting "IS_NUMBER_TRAILING" on the result.

                       int     grok_number_flags(const char *pv, STRLEN len,
                                                 UV *valuep, U32 flags)

       grok_numeric_radix
               Scan and skip for a numeric decimal separator (radix).

                       bool    grok_numeric_radix(const char **sp,
                                                  const char *send)

       grok_oct
               converts a string representing an octal number to numeric form.

               On entry "start" and *len give the string to scan, *flags gives conversion flags,
               and "result" should be "NULL" or a pointer to an NV.  The scan stops at the end of
               the string, or the first invalid character.  Unless "PERL_SCAN_SILENT_ILLDIGIT" is
               set in *flags, encountering an 8 or 9 will also trigger a warning.  On return *len
               is set to the length of the scanned string, and *flags gives output flags.

               If the value is <= "UV_MAX" it is returned as a UV, the output flags are clear,
               and nothing is written to *result.  If the value is > "UV_MAX", "grok_oct" returns
               "UV_MAX", sets "PERL_SCAN_GREATER_THAN_UV_MAX" in the output flags, and writes the
               value to *result (or the value is discarded if "result" is "NULL").

               If "PERL_SCAN_ALLOW_UNDERSCORES" is set in *flags then the octal number may use
               "_" characters to separate digits.

                       UV      grok_oct(const char* start, STRLEN* len_p,
                                        I32* flags, NV *result)

       isinfnan
               "Perl_isinfnan()" is utility function that returns true if the NV argument is
               either an infinity or a "NaN", false otherwise.  To test in more detail, use
               "Perl_isinf()" and "Perl_isnan()".

               This is also the logical inverse of Perl_isfinite().

                       bool    isinfnan(NV nv)

       Perl_signbit
               NOTE: this function is experimental and may change or be removed without notice.

               Return a non-zero integer if the sign bit on an NV is set, and 0 if it is not.

               If Configure detects this system has a "signbit()" that will work with our NVs,
               then we just use it via the "#define" in perl.h.  Otherwise, fall back on this
               implementation.  The main use of this function is catching "-0.0".

               "Configure" notes:  This function is called 'Perl_signbit' instead of a plain
               'signbit' because it is easy to imagine a system having a "signbit()" function or
               macro that doesn't happen to work with our particular choice of NVs.  We shouldn't
               just re-"#define" "signbit" as "Perl_signbit" and expect the standard system
               headers to be happy.  Also, this is a no-context function (no "pTHX_") because
               "Perl_signbit()" is usually re-"#defined" in perl.h as a simple macro call to the
               system's "signbit()".  Users should just always call "Perl_signbit()".

                       int     Perl_signbit(NV f)

       scan_bin
               For backwards compatibility.  Use "grok_bin" instead.

                       NV      scan_bin(const char* start, STRLEN len,
                                        STRLEN* retlen)

       scan_hex
               For backwards compatibility.  Use "grok_hex" instead.

                       NV      scan_hex(const char* start, STRLEN len,
                                        STRLEN* retlen)

       scan_oct
               For backwards compatibility.  Use "grok_oct" instead.

                       NV      scan_oct(const char* start, STRLEN len,
                                        STRLEN* retlen)

Obsolete backwards compatibility functions

       Some of these are also deprecated.  You can exclude these from your compiled Perl by
       adding this option to Configure: "-Accflags='-DNO_MATHOMS'"

       custom_op_desc
               Return the description of a given custom op.  This was once used by the "OP_DESC"
               macro, but is no longer: it has only been kept for compatibility, and should not
               be used.

                       const char * custom_op_desc(const OP *o)

       custom_op_name
               Return the name for a given custom op.  This was once used by the "OP_NAME" macro,
               but is no longer: it has only been kept for compatibility, and should not be used.

                       const char * custom_op_name(const OP *o)

       gv_fetchmethod
               See "gv_fetchmethod_autoload".

                       GV*     gv_fetchmethod(HV* stash, const char* name)

       is_utf8_char
               DEPRECATED!  It is planned to remove this function from a future release of Perl.
               Do not use it for new code; remove it from existing code.

               Tests if some arbitrary number of bytes begins in a valid UTF-8 character.  Note
               that an INVARIANT (i.e. ASCII on non-EBCDIC machines) character is a valid UTF-8
               character.  The actual number of bytes in the UTF-8 character will be returned if
               it is valid, otherwise 0.

               This function is deprecated due to the possibility that malformed input could
               cause reading beyond the end of the input buffer.  Use "isUTF8_CHAR" instead.

                       STRLEN  is_utf8_char(const U8 *s)

       is_utf8_char_buf
               This is identical to the macro "isUTF8_CHAR".

                       STRLEN  is_utf8_char_buf(const U8 *buf,
                                                const U8 *buf_end)

       pack_cat
               The engine implementing "pack()" Perl function.  Note: parameters "next_in_list"
               and "flags" are not used.  This call should not be used; use "packlist" instead.

                       void    pack_cat(SV *cat, const char *pat,
                                        const char *patend, SV **beglist,
                                        SV **endlist, SV ***next_in_list,
                                        U32 flags)

       pad_compname_type
               Looks up the type of the lexical variable at position "po" in the currently-
               compiling pad.  If the variable is typed, the stash of the class to which it is
               typed is returned.  If not, "NULL" is returned.

                       HV *    pad_compname_type(PADOFFSET po)

       sv_2pvbyte_nolen
               Return a pointer to the byte-encoded representation of the SV.  May cause the SV
               to be downgraded from UTF-8 as a side-effect.

               Usually accessed via the "SvPVbyte_nolen" macro.

                       char*   sv_2pvbyte_nolen(SV* sv)

       sv_2pvutf8_nolen
               Return a pointer to the UTF-8-encoded representation of the SV.  May cause the SV
               to be upgraded to UTF-8 as a side-effect.

               Usually accessed via the "SvPVutf8_nolen" macro.

                       char*   sv_2pvutf8_nolen(SV* sv)

       sv_2pv_nolen
               Like "sv_2pv()", but doesn't return the length too.  You should usually use the
               macro wrapper "SvPV_nolen(sv)" instead.

                       char*   sv_2pv_nolen(SV* sv)

       sv_catpvn_mg
               Like "sv_catpvn", but also handles 'set' magic.

                       void    sv_catpvn_mg(SV *sv, const char *ptr,
                                            STRLEN len)

       sv_catsv_mg
               Like "sv_catsv", but also handles 'set' magic.

                       void    sv_catsv_mg(SV *dsv, SV *ssv)

       sv_force_normal
               Undo various types of fakery on an SV: if the PV is a shared string, make a
               private copy; if we're a ref, stop refing; if we're a glob, downgrade to an
               "xpvmg".  See also "sv_force_normal_flags".

                       void    sv_force_normal(SV *sv)

       sv_iv   A private implementation of the "SvIVx" macro for compilers which can't cope with
               complex macro expressions.  Always use the macro instead.

                       IV      sv_iv(SV* sv)

       sv_nolocking
               Dummy routine which "locks" an SV when there is no locking module present.  Exists
               to avoid test for a "NULL" function pointer and because it could potentially warn
               under some level of strict-ness.

               "Superseded" by "sv_nosharing()".

                       void    sv_nolocking(SV *sv)

       sv_nounlocking
               Dummy routine which "unlocks" an SV when there is no locking module present.
               Exists to avoid test for a "NULL" function pointer and because it could
               potentially warn under some level of strict-ness.

               "Superseded" by "sv_nosharing()".

                       void    sv_nounlocking(SV *sv)

       sv_nv   A private implementation of the "SvNVx" macro for compilers which can't cope with
               complex macro expressions.  Always use the macro instead.

                       NV      sv_nv(SV* sv)

       sv_pv   Use the "SvPV_nolen" macro instead

                       char*   sv_pv(SV *sv)

       sv_pvbyte
               Use "SvPVbyte_nolen" instead.

                       char*   sv_pvbyte(SV *sv)

       sv_pvbyten
               A private implementation of the "SvPVbyte" macro for compilers which can't cope
               with complex macro expressions.  Always use the macro instead.

                       char*   sv_pvbyten(SV *sv, STRLEN *lp)

       sv_pvn  A private implementation of the "SvPV" macro for compilers which can't cope with
               complex macro expressions.  Always use the macro instead.

                       char*   sv_pvn(SV *sv, STRLEN *lp)

       sv_pvutf8
               Use the "SvPVutf8_nolen" macro instead

                       char*   sv_pvutf8(SV *sv)

       sv_pvutf8n
               A private implementation of the "SvPVutf8" macro for compilers which can't cope
               with complex macro expressions.  Always use the macro instead.

                       char*   sv_pvutf8n(SV *sv, STRLEN *lp)

       sv_taint
               Taint an SV.  Use "SvTAINTED_on" instead.

                       void    sv_taint(SV* sv)

       sv_unref
               Unsets the RV status of the SV, and decrements the reference count of whatever was
               being referenced by the RV.  This can almost be thought of as a reversal of
               "newSVrv".  This is "sv_unref_flags" with the "flag" being zero.  See "SvROK_off".

                       void    sv_unref(SV* sv)

       sv_usepvn
               Tells an SV to use "ptr" to find its string value.  Implemented by calling
               "sv_usepvn_flags" with "flags" of 0, hence does not handle 'set' magic.  See
               "sv_usepvn_flags".

                       void    sv_usepvn(SV* sv, char* ptr, STRLEN len)

       sv_usepvn_mg
               Like "sv_usepvn", but also handles 'set' magic.

                       void    sv_usepvn_mg(SV *sv, char *ptr, STRLEN len)

       sv_uv   A private implementation of the "SvUVx" macro for compilers which can't cope with
               complex macro expressions.  Always use the macro instead.

                       UV      sv_uv(SV* sv)

       unpack_str
               The engine implementing "unpack()" Perl function.  Note: parameters "strbeg",
               "new_s" and "ocnt" are not used.  This call should not be used, use "unpackstring"
               instead.

                       I32     unpack_str(const char *pat, const char *patend,
                                          const char *s, const char *strbeg,
                                          const char *strend, char **new_s,
                                          I32 ocnt, U32 flags)

       utf8_to_uvchr
               DEPRECATED!  It is planned to remove this function from a future release of Perl.
               Do not use it for new code; remove it from existing code.

               Returns the native code point of the first character in the string "s" which is
               assumed to be in UTF-8 encoding; "retlen" will be set to the length, in bytes, of
               that character.

               Some, but not all, UTF-8 malformations are detected, and in fact, some malformed
               input could cause reading beyond the end of the input buffer, which is why this
               function is deprecated.  Use "utf8_to_uvchr_buf" instead.

               If "s" points to one of the detected malformations, and UTF8 warnings are enabled,
               zero is returned and *retlen is set (if "retlen" isn't "NULL") to -1.  If those
               warnings are off, the computed value if well-defined (or the Unicode REPLACEMENT
               CHARACTER, if not) is silently returned, and *retlen is set (if "retlen" isn't
               NULL) so that ("s" + *retlen) is the next possible position in "s" that could
               begin a non-malformed character.  See "utf8n_to_uvchr" for details on when the
               REPLACEMENT CHARACTER is returned.

                       UV      utf8_to_uvchr(const U8 *s, STRLEN *retlen)

       utf8_to_uvuni
               DEPRECATED!  It is planned to remove this function from a future release of Perl.
               Do not use it for new code; remove it from existing code.

               Returns the Unicode code point of the first character in the string "s" which is
               assumed to be in UTF-8 encoding; "retlen" will be set to the length, in bytes, of
               that character.

               Some, but not all, UTF-8 malformations are detected, and in fact, some malformed
               input could cause reading beyond the end of the input buffer, which is one reason
               why this function is deprecated.  The other is that only in extremely limited
               circumstances should the Unicode versus native code point be of any interest to
               you.  See "utf8_to_uvuni_buf" for alternatives.

               If "s" points to one of the detected malformations, and UTF8 warnings are enabled,
               zero is returned and *retlen is set (if "retlen" doesn't point to NULL) to -1.  If
               those warnings are off, the computed value if well-defined (or the Unicode
               REPLACEMENT CHARACTER, if not) is silently returned, and *retlen is set (if
               "retlen" isn't NULL) so that ("s" + *retlen) is the next possible position in "s"
               that could begin a non-malformed character.  See "utf8n_to_uvchr" for details on
               when the REPLACEMENT CHARACTER is returned.

                       UV      utf8_to_uvuni(const U8 *s, STRLEN *retlen)

Optree construction

       newASSIGNOP
               Constructs, checks, and returns an assignment op.  "left" and "right" supply the
               parameters of the assignment; they are consumed by this function and become part
               of the constructed op tree.

               If "optype" is "OP_ANDASSIGN", "OP_ORASSIGN", or "OP_DORASSIGN", then a suitable
               conditional optree is constructed.  If "optype" is the opcode of a binary
               operator, such as "OP_BIT_OR", then an op is constructed that performs the binary
               operation and assigns the result to the left argument.  Either way, if "optype" is
               non-zero then "flags" has no effect.

               If "optype" is zero, then a plain scalar or list assignment is constructed.  Which
               type of assignment it is is automatically determined.  "flags" gives the eight
               bits of "op_flags", except that "OPf_KIDS" will be set automatically, and, shifted
               up eight bits, the eight bits of "op_private", except that the bit with value 1 or
               2 is automatically set as required.

                       OP *    newASSIGNOP(I32 flags, OP *left, I32 optype,
                                           OP *right)

       newBINOP
               Constructs, checks, and returns an op of any binary type.  "type" is the opcode.
               "flags" gives the eight bits of "op_flags", except that "OPf_KIDS" will be set
               automatically, and, shifted up eight bits, the eight bits of "op_private", except
               that the bit with value 1 or 2 is automatically set as required.  "first" and
               "last" supply up to two ops to be the direct children of the binary op; they are
               consumed by this function and become part of the constructed op tree.

                       OP *    newBINOP(I32 type, I32 flags, OP *first,
                                        OP *last)

       newCONDOP
               Constructs, checks, and returns a conditional-expression ("cond_expr") op.
               "flags" gives the eight bits of "op_flags", except that "OPf_KIDS" will be set
               automatically, and, shifted up eight bits, the eight bits of "op_private", except
               that the bit with value 1 is automatically set.  "first" supplies the expression
               selecting between the two branches, and "trueop" and "falseop" supply the
               branches; they are consumed by this function and become part of the constructed op
               tree.

                       OP *    newCONDOP(I32 flags, OP *first, OP *trueop,
                                         OP *falseop)

       newDEFSVOP
               Constructs and returns an op to access $_.

                       OP *    newDEFSVOP()

       newFOROP
               Constructs, checks, and returns an op tree expressing a "foreach" loop (iteration
               through a list of values).  This is a heavyweight loop, with structure that allows
               exiting the loop by "last" and suchlike.

               "sv" optionally supplies the variable that will be aliased to each item in turn;
               if null, it defaults to $_.  "expr" supplies the list of values to iterate over.
               "block" supplies the main body of the loop, and "cont" optionally supplies a
               "continue" block that operates as a second half of the body.  All of these optree
               inputs are consumed by this function and become part of the constructed op tree.

               "flags" gives the eight bits of "op_flags" for the "leaveloop" op and, shifted up
               eight bits, the eight bits of "op_private" for the "leaveloop" op, except that (in
               both cases) some bits will be set automatically.

                       OP *    newFOROP(I32 flags, OP *sv, OP *expr, OP *block,
                                        OP *cont)

       newGIVENOP
               Constructs, checks, and returns an op tree expressing a "given" block.  "cond"
               supplies the expression that will be locally assigned to a lexical variable, and
               "block" supplies the body of the "given" construct; they are consumed by this
               function and become part of the constructed op tree.  "defsv_off" must be zero (it
               used to identity the pad slot of lexical $_).

                       OP *    newGIVENOP(OP *cond, OP *block,
                                          PADOFFSET defsv_off)

       newGVOP Constructs, checks, and returns an op of any type that involves an embedded
               reference to a GV.  "type" is the opcode.  "flags" gives the eight bits of
               "op_flags".  "gv" identifies the GV that the op should reference; calling this
               function does not transfer ownership of any reference to it.

                       OP *    newGVOP(I32 type, I32 flags, GV *gv)

       newLISTOP
               Constructs, checks, and returns an op of any list type.  "type" is the opcode.
               "flags" gives the eight bits of "op_flags", except that "OPf_KIDS" will be set
               automatically if required.  "first" and "last" supply up to two ops to be direct
               children of the list op; they are consumed by this function and become part of the
               constructed op tree.

               For most list operators, the check function expects all the kid ops to be present
               already, so calling "newLISTOP(OP_JOIN, ...)" (e.g.) is not appropriate.  What you
               want to do in that case is create an op of type "OP_LIST", append more children to
               it, and then call "op_convert_list".  See "op_convert_list" for more information.

                       OP *    newLISTOP(I32 type, I32 flags, OP *first,
                                         OP *last)

       newLOGOP
               Constructs, checks, and returns a logical (flow control) op.  "type" is the
               opcode.  "flags" gives the eight bits of "op_flags", except that "OPf_KIDS" will
               be set automatically, and, shifted up eight bits, the eight bits of "op_private",
               except that the bit with value 1 is automatically set.  "first" supplies the
               expression controlling the flow, and "other" supplies the side (alternate) chain
               of ops; they are consumed by this function and become part of the constructed op
               tree.

                       OP *    newLOGOP(I32 type, I32 flags, OP *first,
                                        OP *other)

       newLOOPEX
               Constructs, checks, and returns a loop-exiting op (such as "goto" or "last").
               "type" is the opcode.  "label" supplies the parameter determining the target of
               the op; it is consumed by this function and becomes part of the constructed op
               tree.

                       OP *    newLOOPEX(I32 type, OP *label)

       newLOOPOP
               Constructs, checks, and returns an op tree expressing a loop.  This is only a loop
               in the control flow through the op tree; it does not have the heavyweight loop
               structure that allows exiting the loop by "last" and suchlike.  "flags" gives the
               eight bits of "op_flags" for the top-level op, except that some bits will be set
               automatically as required.  "expr" supplies the expression controlling loop
               iteration, and "block" supplies the body of the loop; they are consumed by this
               function and become part of the constructed op tree.  "debuggable" is currently
               unused and should always be 1.

                       OP *    newLOOPOP(I32 flags, I32 debuggable, OP *expr,
                                         OP *block)

       newMETHOP
               Constructs, checks, and returns an op of method type with a method name evaluated
               at runtime.  "type" is the opcode.  "flags" gives the eight bits of "op_flags",
               except that "OPf_KIDS" will be set automatically, and, shifted up eight bits, the
               eight bits of "op_private", except that the bit with value 1 is automatically set.
               "dynamic_meth" supplies an op which evaluates method name; it is consumed by this
               function and become part of the constructed op tree.  Supported optypes:
               "OP_METHOD".

                       OP *    newMETHOP(I32 type, I32 flags, OP *first)

       newMETHOP_named
               Constructs, checks, and returns an op of method type with a constant method name.
               "type" is the opcode.  "flags" gives the eight bits of "op_flags", and, shifted up
               eight bits, the eight bits of "op_private".  "const_meth" supplies a constant
               method name; it must be a shared COW string.  Supported optypes:
               "OP_METHOD_NAMED".

                       OP *    newMETHOP_named(I32 type, I32 flags,
                                               SV *const_meth)

       newNULLLIST
               Constructs, checks, and returns a new "stub" op, which represents an empty list
               expression.

                       OP *    newNULLLIST()

       newOP   Constructs, checks, and returns an op of any base type (any type that has no extra
               fields).  "type" is the opcode.  "flags" gives the eight bits of "op_flags", and,
               shifted up eight bits, the eight bits of "op_private".

                       OP *    newOP(I32 type, I32 flags)

       newPADOP
               Constructs, checks, and returns an op of any type that involves a reference to a
               pad element.  "type" is the opcode.  "flags" gives the eight bits of "op_flags".
               A pad slot is automatically allocated, and is populated with "sv"; this function
               takes ownership of one reference to it.

               This function only exists if Perl has been compiled to use ithreads.

                       OP *    newPADOP(I32 type, I32 flags, SV *sv)

       newPMOP Constructs, checks, and returns an op of any pattern matching type.  "type" is the
               opcode.  "flags" gives the eight bits of "op_flags" and, shifted up eight bits,
               the eight bits of "op_private".

                       OP *    newPMOP(I32 type, I32 flags)

       newPVOP Constructs, checks, and returns an op of any type that involves an embedded
               C-level pointer (PV).  "type" is the opcode.  "flags" gives the eight bits of
               "op_flags".  "pv" supplies the C-level pointer, which must have been allocated
               using "PerlMemShared_malloc"; the memory will be freed when the op is destroyed.

                       OP *    newPVOP(I32 type, I32 flags, char *pv)

       newRANGE
               Constructs and returns a "range" op, with subordinate "flip" and "flop" ops.
               "flags" gives the eight bits of "op_flags" for the "flip" op and, shifted up eight
               bits, the eight bits of "op_private" for both the "flip" and "range" ops, except
               that the bit with value 1 is automatically set.  "left" and "right" supply the
               expressions controlling the endpoints of the range; they are consumed by this
               function and become part of the constructed op tree.

                       OP *    newRANGE(I32 flags, OP *left, OP *right)

       newSLICEOP
               Constructs, checks, and returns an "lslice" (list slice) op.  "flags" gives the
               eight bits of "op_flags", except that "OPf_KIDS" will be set automatically, and,
               shifted up eight bits, the eight bits of "op_private", except that the bit with
               value 1 or 2 is automatically set as required.  "listval" and "subscript" supply
               the parameters of the slice; they are consumed by this function and become part of
               the constructed op tree.

                       OP *    newSLICEOP(I32 flags, OP *subscript,
                                          OP *listval)

       newSTATEOP
               Constructs a state op (COP).  The state op is normally a "nextstate" op, but will
               be a "dbstate" op if debugging is enabled for currently-compiled code.  The state
               op is populated from "PL_curcop" (or "PL_compiling").  If "label" is non-null, it
               supplies the name of a label to attach to the state op; this function takes
               ownership of the memory pointed at by "label", and will free it.  "flags" gives
               the eight bits of "op_flags" for the state op.

               If "o" is null, the state op is returned.  Otherwise the state op is combined with
               "o" into a "lineseq" list op, which is returned.  "o" is consumed by this function
               and becomes part of the returned op tree.

                       OP *    newSTATEOP(I32 flags, char *label, OP *o)

       newSVOP Constructs, checks, and returns an op of any type that involves an embedded SV.
               "type" is the opcode.  "flags" gives the eight bits of "op_flags".  "sv" gives the
               SV to embed in the op; this function takes ownership of one reference to it.

                       OP *    newSVOP(I32 type, I32 flags, SV *sv)

       newUNOP Constructs, checks, and returns an op of any unary type.  "type" is the opcode.
               "flags" gives the eight bits of "op_flags", except that "OPf_KIDS" will be set
               automatically if required, and, shifted up eight bits, the eight bits of
               "op_private", except that the bit with value 1 is automatically set.  "first"
               supplies an optional op to be the direct child of the unary op; it is consumed by
               this function and become part of the constructed op tree.

                       OP *    newUNOP(I32 type, I32 flags, OP *first)

       newUNOP_AUX
               Similar to "newUNOP", but creates an "UNOP_AUX" struct instead, with "op_aux"
               initialised to "aux"

                       OP*     newUNOP_AUX(I32 type, I32 flags, OP* first,
                                           UNOP_AUX_item *aux)

       newWHENOP
               Constructs, checks, and returns an op tree expressing a "when" block.  "cond"
               supplies the test expression, and "block" supplies the block that will be executed
               if the test evaluates to true; they are consumed by this function and become part
               of the constructed op tree.  "cond" will be interpreted DWIMically, often as a
               comparison against $_, and may be null to generate a "default" block.

                       OP *    newWHENOP(OP *cond, OP *block)

       newWHILEOP
               Constructs, checks, and returns an op tree expressing a "while" loop.  This is a
               heavyweight loop, with structure that allows exiting the loop by "last" and
               suchlike.

               "loop" is an optional preconstructed "enterloop" op to use in the loop; if it is
               null then a suitable op will be constructed automatically.  "expr" supplies the
               loop's controlling expression.  "block" supplies the main body of the loop, and
               "cont" optionally supplies a "continue" block that operates as a second half of
               the body.  All of these optree inputs are consumed by this function and become
               part of the constructed op tree.

               "flags" gives the eight bits of "op_flags" for the "leaveloop" op and, shifted up
               eight bits, the eight bits of "op_private" for the "leaveloop" op, except that (in
               both cases) some bits will be set automatically.  "debuggable" is currently unused
               and should always be 1.  "has_my" can be supplied as true to force the loop body
               to be enclosed in its own scope.

                       OP *    newWHILEOP(I32 flags, I32 debuggable,
                                          LOOP *loop, OP *expr, OP *block,
                                          OP *cont, I32 has_my)

Optree Manipulation Functions

       alloccopstash
               NOTE: this function is experimental and may change or be removed without notice.

               Available only under threaded builds, this function allocates an entry in
               "PL_stashpad" for the stash passed to it.

                       PADOFFSET alloccopstash(HV *hv)

       block_end
               Handles compile-time scope exit.  "floor" is the savestack index returned by
               "block_start", and "seq" is the body of the block.  Returns the block, possibly
               modified.

                       OP *    block_end(I32 floor, OP *seq)

       block_start
               Handles compile-time scope entry.  Arranges for hints to be restored on block exit
               and also handles pad sequence numbers to make lexical variables scope right.
               Returns a savestack index for use with "block_end".

                       int     block_start(int full)

       ck_entersub_args_list
               Performs the default fixup of the arguments part of an "entersub" op tree.  This
               consists of applying list context to each of the argument ops.  This is the
               standard treatment used on a call marked with "&", or a method call, or a call
               through a subroutine reference, or any other call where the callee can't be
               identified at compile time, or a call where the callee has no prototype.

                       OP *    ck_entersub_args_list(OP *entersubop)

       ck_entersub_args_proto
               Performs the fixup of the arguments part of an "entersub" op tree based on a
               subroutine prototype.  This makes various modifications to the argument ops, from
               applying context up to inserting "refgen" ops, and checking the number and
               syntactic types of arguments, as directed by the prototype.  This is the standard
               treatment used on a subroutine call, not marked with "&", where the callee can be
               identified at compile time and has a prototype.

               "protosv" supplies the subroutine prototype to be applied to the call.  It may be
               a normal defined scalar, of which the string value will be used.  Alternatively,
               for convenience, it may be a subroutine object (a "CV*" that has been cast to
               "SV*") which has a prototype.  The prototype supplied, in whichever form, does not
               need to match the actual callee referenced by the op tree.

               If the argument ops disagree with the prototype, for example by having an
               unacceptable number of arguments, a valid op tree is returned anyway.  The error
               is reflected in the parser state, normally resulting in a single exception at the
               top level of parsing which covers all the compilation errors that occurred.  In
               the error message, the callee is referred to by the name defined by the "namegv"
               parameter.

                       OP *    ck_entersub_args_proto(OP *entersubop,
                                                      GV *namegv, SV *protosv)

       ck_entersub_args_proto_or_list
               Performs the fixup of the arguments part of an "entersub" op tree either based on
               a subroutine prototype or using default list-context processing.  This is the
               standard treatment used on a subroutine call, not marked with "&", where the
               callee can be identified at compile time.

               "protosv" supplies the subroutine prototype to be applied to the call, or
               indicates that there is no prototype.  It may be a normal scalar, in which case if
               it is defined then the string value will be used as a prototype, and if it is
               undefined then there is no prototype.  Alternatively, for convenience, it may be a
               subroutine object (a "CV*" that has been cast to "SV*"), of which the prototype
               will be used if it has one.  The prototype (or lack thereof) supplied, in
               whichever form, does not need to match the actual callee referenced by the op
               tree.

               If the argument ops disagree with the prototype, for example by having an
               unacceptable number of arguments, a valid op tree is returned anyway.  The error
               is reflected in the parser state, normally resulting in a single exception at the
               top level of parsing which covers all the compilation errors that occurred.  In
               the error message, the callee is referred to by the name defined by the "namegv"
               parameter.

                       OP *    ck_entersub_args_proto_or_list(OP *entersubop,
                                                              GV *namegv,
                                                              SV *protosv)

       cv_const_sv
               If "cv" is a constant sub eligible for inlining, returns the constant value
               returned by the sub.  Otherwise, returns "NULL".

               Constant subs can be created with "newCONSTSUB" or as described in "Constant
               Functions" in perlsub.

                       SV*     cv_const_sv(const CV *const cv)

       cv_get_call_checker
               Retrieves the function that will be used to fix up a call to "cv".  Specifically,
               the function is applied to an "entersub" op tree for a subroutine call, not marked
               with "&", where the callee can be identified at compile time as "cv".

               The C-level function pointer is returned in *ckfun_p, and an SV argument for it is
               returned in *ckobj_p.  The function is intended to be called in this manner:

                entersubop = (*ckfun_p)(aTHX_ entersubop, namegv, (*ckobj_p));

               In this call, "entersubop" is a pointer to the "entersub" op, which may be
               replaced by the check function, and "namegv" is a GV supplying the name that
               should be used by the check function to refer to the callee of the "entersub" op
               if it needs to emit any diagnostics.  It is permitted to apply the check function
               in non-standard situations, such as to a call to a different subroutine or to a
               method call.

               By default, the function is Perl_ck_entersub_args_proto_or_list, and the SV
               parameter is "cv" itself.  This implements standard prototype processing.  It can
               be changed, for a particular subroutine, by "cv_set_call_checker".

                       void    cv_get_call_checker(CV *cv,
                                                   Perl_call_checker *ckfun_p,
                                                   SV **ckobj_p)

       cv_set_call_checker
               The original form of "cv_set_call_checker_flags", which passes it the
               "CALL_CHECKER_REQUIRE_GV" flag for backward-compatibility.

                       void    cv_set_call_checker(CV *cv,
                                                   Perl_call_checker ckfun,
                                                   SV *ckobj)

       cv_set_call_checker_flags
               Sets the function that will be used to fix up a call to "cv".  Specifically, the
               function is applied to an "entersub" op tree for a subroutine call, not marked
               with "&", where the callee can be identified at compile time as "cv".

               The C-level function pointer is supplied in "ckfun", and an SV argument for it is
               supplied in "ckobj".  The function should be defined like this:

                   STATIC OP * ckfun(pTHX_ OP *op, GV *namegv, SV *ckobj)

               It is intended to be called in this manner:

                   entersubop = ckfun(aTHX_ entersubop, namegv, ckobj);

               In this call, "entersubop" is a pointer to the "entersub" op, which may be
               replaced by the check function, and "namegv" supplies the name that should be used
               by the check function to refer to the callee of the "entersub" op if it needs to
               emit any diagnostics.  It is permitted to apply the check function in non-standard
               situations, such as to a call to a different subroutine or to a method call.

               "namegv" may not actually be a GV.  For efficiency, perl may pass a CV or other SV
               instead.  Whatever is passed can be used as the first argument to "cv_name".  You
               can force perl to pass a GV by including "CALL_CHECKER_REQUIRE_GV" in the "flags".

               The current setting for a particular CV can be retrieved by "cv_get_call_checker".

                       void    cv_set_call_checker_flags(
                                   CV *cv, Perl_call_checker ckfun, SV *ckobj,
                                   U32 flags
                               )

       LINKLIST
               Given the root of an optree, link the tree in execution order using the "op_next"
               pointers and return the first op executed.  If this has already been done, it will
               not be redone, and "o->op_next" will be returned.  If "o->op_next" is not already
               set, "o" should be at least an "UNOP".

                       OP*     LINKLIST(OP *o)

       newCONSTSUB
               See "newCONSTSUB_flags".

                       CV*     newCONSTSUB(HV* stash, const char* name, SV* sv)

       newCONSTSUB_flags
               Creates a constant sub equivalent to Perl "sub FOO () { 123 }" which is eligible
               for inlining at compile-time.

               Currently, the only useful value for "flags" is "SVf_UTF8".

               The newly created subroutine takes ownership of a reference to the passed in SV.

               Passing "NULL" for SV creates a constant sub equivalent to "sub BAR () {}", which
               won't be called if used as a destructor, but will suppress the overhead of a call
               to "AUTOLOAD".  (This form, however, isn't eligible for inlining at compile time.)

                       CV*     newCONSTSUB_flags(HV* stash, const char* name,
                                                 STRLEN len, U32 flags, SV* sv)

       newXS   Used by "xsubpp" to hook up XSUBs as Perl subs.  "filename" needs to be static
               storage, as it is used directly as CvFILE(), without a copy being made.

       op_append_elem
               Append an item to the list of ops contained directly within a list-type op,
               returning the lengthened list.  "first" is the list-type op, and "last" is the op
               to append to the list.  "optype" specifies the intended opcode for the list.  If
               "first" is not already a list of the right type, it will be upgraded into one.  If
               either "first" or "last" is null, the other is returned unchanged.

                       OP *    op_append_elem(I32 optype, OP *first, OP *last)

       op_append_list
               Concatenate the lists of ops contained directly within two list-type ops,
               returning the combined list.  "first" and "last" are the list-type ops to
               concatenate.  "optype" specifies the intended opcode for the list.  If either
               "first" or "last" is not already a list of the right type, it will be upgraded
               into one.  If either "first" or "last" is null, the other is returned unchanged.

                       OP *    op_append_list(I32 optype, OP *first, OP *last)

       OP_CLASS
               Return the class of the provided OP: that is, which of the *OP structures it uses.
               For core ops this currently gets the information out of "PL_opargs", which does
               not always accurately reflect the type used; in v5.26 onwards, see also the
               function "op_class" which can do a better job of determining the used type.

               For custom ops the type is returned from the registration, and it is up to the
               registree to ensure it is accurate.  The value returned will be one of the "OA_"*
               constants from op.h.

                       U32     OP_CLASS(OP *o)

       op_contextualize
               Applies a syntactic context to an op tree representing an expression.  "o" is the
               op tree, and "context" must be "G_SCALAR", "G_ARRAY", or "G_VOID" to specify the
               context to apply.  The modified op tree is returned.

                       OP *    op_contextualize(OP *o, I32 context)

       op_convert_list
               Converts "o" into a list op if it is not one already, and then converts it into
               the specified "type", calling its check function, allocating a target if it needs
               one, and folding constants.

               A list-type op is usually constructed one kid at a time via "newLISTOP",
               "op_prepend_elem" and "op_append_elem".  Then finally it is passed to
               "op_convert_list" to make it the right type.

                       OP *    op_convert_list(I32 type, I32 flags, OP *o)

       OP_DESC Return a short description of the provided OP.

                       const char * OP_DESC(OP *o)

       op_free Free an op.  Only use this when an op is no longer linked to from any optree.

                       void    op_free(OP *o)

       OpHAS_SIBLING
               Returns true if "o" has a sibling

                       bool    OpHAS_SIBLING(OP *o)

       OpLASTSIB_set
               Marks "o" as having no further siblings. On "PERL_OP_PARENT" builds, marks o as
               having the specified parent. See also "OpMORESIB_set" and "OpMAYBESIB_set". For a
               higher-level interface, see "op_sibling_splice".

                       void    OpLASTSIB_set(OP *o, OP *parent)

       op_linklist
               This function is the implementation of the "LINKLIST" macro.  It should not be
               called directly.

                       OP*     op_linklist(OP *o)

       op_lvalue
               NOTE: this function is experimental and may change or be removed without notice.

               Propagate lvalue ("modifiable") context to an op and its children.  "type"
               represents the context type, roughly based on the type of op that would do the
               modifying, although "local()" is represented by "OP_NULL", because it has no op
               type of its own (it is signalled by a flag on the lvalue op).

               This function detects things that can't be modified, such as "$x+1", and generates
               errors for them.  For example, "$x+1 = 2" would cause it to be called with an op
               of type "OP_ADD" and a "type" argument of "OP_SASSIGN".

               It also flags things that need to behave specially in an lvalue context, such as
               "$$x = 5" which might have to vivify a reference in $x.

                       OP *    op_lvalue(OP *o, I32 type)

       OpMAYBESIB_set
               Conditionally does "OpMORESIB_set" or "OpLASTSIB_set" depending on whether "sib"
               is non-null. For a higher-level interface, see "op_sibling_splice".

                       void    OpMAYBESIB_set(OP *o, OP *sib, OP *parent)

       OpMORESIB_set
               Sets the sibling of "o" to the non-zero value "sib". See also "OpLASTSIB_set" and
               "OpMAYBESIB_set". For a higher-level interface, see "op_sibling_splice".

                       void    OpMORESIB_set(OP *o, OP *sib)

       OP_NAME Return the name of the provided OP.  For core ops this looks up the name from the
               op_type; for custom ops from the op_ppaddr.

                       const char * OP_NAME(OP *o)

       op_null Neutralizes an op when it is no longer needed, but is still linked to from other
               ops.

                       void    op_null(OP *o)

       op_parent
               Returns the parent OP of "o", if it has a parent. Returns "NULL" otherwise.  This
               function is only available on perls built with "-DPERL_OP_PARENT".

                       OP*     op_parent(OP *o)

       op_prepend_elem
               Prepend an item to the list of ops contained directly within a list-type op,
               returning the lengthened list.  "first" is the op to prepend to the list, and
               "last" is the list-type op.  "optype" specifies the intended opcode for the list.
               If "last" is not already a list of the right type, it will be upgraded into one.
               If either "first" or "last" is null, the other is returned unchanged.

                       OP *    op_prepend_elem(I32 optype, OP *first, OP *last)

       op_scope
               NOTE: this function is experimental and may change or be removed without notice.

               Wraps up an op tree with some additional ops so that at runtime a dynamic scope
               will be created.  The original ops run in the new dynamic scope, and then,
               provided that they exit normally, the scope will be unwound.  The additional ops
               used to create and unwind the dynamic scope will normally be an "enter"/"leave"
               pair, but a "scope" op may be used instead if the ops are simple enough to not
               need the full dynamic scope structure.

                       OP *    op_scope(OP *o)

       OpSIBLING
               Returns the sibling of "o", or "NULL" if there is no sibling

                       OP*     OpSIBLING(OP *o)

       op_sibling_splice
               A general function for editing the structure of an existing chain of op_sibling
               nodes.  By analogy with the perl-level "splice()" function, allows you to delete
               zero or more sequential nodes, replacing them with zero or more different nodes.
               Performs the necessary op_first/op_last housekeeping on the parent node and
               op_sibling manipulation on the children.  The last deleted node will be marked as
               as the last node by updating the op_sibling/op_sibparent or op_moresib field as
               appropriate.

               Note that op_next is not manipulated, and nodes are not freed; that is the
               responsibility of the caller.  It also won't create a new list op for an empty
               list etc; use higher-level functions like op_append_elem() for that.

               "parent" is the parent node of the sibling chain. It may passed as "NULL" if the
               splicing doesn't affect the first or last op in the chain.

               "start" is the node preceding the first node to be spliced.  Node(s) following it
               will be deleted, and ops will be inserted after it.  If it is "NULL", the first
               node onwards is deleted, and nodes are inserted at the beginning.

               "del_count" is the number of nodes to delete.  If zero, no nodes are deleted.  If
               -1 or greater than or equal to the number of remaining kids, all remaining kids
               are deleted.

               "insert" is the first of a chain of nodes to be inserted in place of the nodes.
               If "NULL", no nodes are inserted.

               The head of the chain of deleted ops is returned, or "NULL" if no ops were
               deleted.

               For example:

                   action                    before      after         returns
                   ------                    -----       -----         -------

                                             P           P
                   splice(P, A, 2, X-Y-Z)    |           |             B-C
                                             A-B-C-D     A-X-Y-Z-D

                                             P           P
                   splice(P, NULL, 1, X-Y)   |           |             A
                                             A-B-C-D     X-Y-B-C-D

                                             P           P
                   splice(P, NULL, 3, NULL)  |           |             A-B-C
                                             A-B-C-D     D

                                             P           P
                   splice(P, B, 0, X-Y)      |           |             NULL
                                             A-B-C-D     A-B-X-Y-C-D

               For lower-level direct manipulation of "op_sibparent" and "op_moresib", see
               "OpMORESIB_set", "OpLASTSIB_set", "OpMAYBESIB_set".

                       OP*     op_sibling_splice(OP *parent, OP *start,
                                                 int del_count, OP* insert)

       OP_TYPE_IS
               Returns true if the given OP is not a "NULL" pointer and if it is of the given
               type.

               The negation of this macro, "OP_TYPE_ISNT" is also available as well as
               "OP_TYPE_IS_NN" and "OP_TYPE_ISNT_NN" which elide the NULL pointer check.

                       bool    OP_TYPE_IS(OP *o, Optype type)

       OP_TYPE_IS_OR_WAS
               Returns true if the given OP is not a NULL pointer and if it is of the given type
               or used to be before being replaced by an OP of type OP_NULL.

               The negation of this macro, "OP_TYPE_ISNT_AND_WASNT" is also available as well as
               "OP_TYPE_IS_OR_WAS_NN" and "OP_TYPE_ISNT_AND_WASNT_NN" which elide the "NULL"
               pointer check.

                       bool    OP_TYPE_IS_OR_WAS(OP *o, Optype type)

       rv2cv_op_cv
               Examines an op, which is expected to identify a subroutine at runtime, and
               attempts to determine at compile time which subroutine it identifies.  This is
               normally used during Perl compilation to determine whether a prototype can be
               applied to a function call.  "cvop" is the op being considered, normally an
               "rv2cv" op.  A pointer to the identified subroutine is returned, if it could be
               determined statically, and a null pointer is returned if it was not possible to
               determine statically.

               Currently, the subroutine can be identified statically if the RV that the "rv2cv"
               is to operate on is provided by a suitable "gv" or "const" op.  A "gv" op is
               suitable if the GV's CV slot is populated.  A "const" op is suitable if the
               constant value must be an RV pointing to a CV.  Details of this process may change
               in future versions of Perl.  If the "rv2cv" op has the "OPpENTERSUB_AMPER" flag
               set then no attempt is made to identify the subroutine statically: this flag is
               used to suppress compile-time magic on a subroutine call, forcing it to use
               default runtime behaviour.

               If "flags" has the bit "RV2CVOPCV_MARK_EARLY" set, then the handling of a GV
               reference is modified.  If a GV was examined and its CV slot was found to be
               empty, then the "gv" op has the "OPpEARLY_CV" flag set.  If the op is not
               optimised away, and the CV slot is later populated with a subroutine having a
               prototype, that flag eventually triggers the warning "called too early to check
               prototype".

               If "flags" has the bit "RV2CVOPCV_RETURN_NAME_GV" set, then instead of returning a
               pointer to the subroutine it returns a pointer to the GV giving the most
               appropriate name for the subroutine in this context.  Normally this is just the
               "CvGV" of the subroutine, but for an anonymous ("CvANON") subroutine that is
               referenced through a GV it will be the referencing GV.  The resulting "GV*" is
               cast to "CV*" to be returned.  A null pointer is returned as usual if there is no
               statically-determinable subroutine.

                       CV *    rv2cv_op_cv(OP *cvop, U32 flags)

Pack and Unpack

       packlist
               The engine implementing "pack()" Perl function.

                       void    packlist(SV *cat, const char *pat,
                                        const char *patend, SV **beglist,
                                        SV **endlist)

       unpackstring
               The engine implementing the "unpack()" Perl function.

               Using the template "pat..patend", this function unpacks the string "s..strend"
               into a number of mortal SVs, which it pushes onto the perl argument (@_) stack (so
               you will need to issue a "PUTBACK" before and "SPAGAIN" after the call to this
               function).  It returns the number of pushed elements.

               The "strend" and "patend" pointers should point to the byte following the last
               character of each string.

               Although this function returns its values on the perl argument stack, it doesn't
               take any parameters from that stack (and thus in particular there's no need to do
               a "PUSHMARK" before calling it, unlike "call_pv" for example).

                       I32     unpackstring(const char *pat,
                                            const char *patend, const char *s,
                                            const char *strend, U32 flags)

Pad Data Structures

       CvPADLIST
               NOTE: this function is experimental and may change or be removed without notice.

               CV's can have CvPADLIST(cv) set to point to a PADLIST.  This is the CV's
               scratchpad, which stores lexical variables and opcode temporary and per-thread
               values.

               For these purposes "formats" are a kind-of CV; eval""s are too (except they're not
               callable at will and are always thrown away after the eval"" is done executing).
               Require'd files are simply evals without any outer lexical scope.

               XSUBs do not have a "CvPADLIST".  "dXSTARG" fetches values from "PL_curpad", but
               that is really the callers pad (a slot of which is allocated by every entersub).
               Do not get or set "CvPADLIST" if a CV is an XSUB (as determined by "CvISXSUB()"),
               "CvPADLIST" slot is reused for a different internal purpose in XSUBs.

               The PADLIST has a C array where pads are stored.

               The 0th entry of the PADLIST is a PADNAMELIST which represents the "names" or
               rather the "static type information" for lexicals.  The individual elements of a
               PADNAMELIST are PADNAMEs.  Future refactorings might stop the PADNAMELIST from
               being stored in the PADLIST's array, so don't rely on it.  See "PadlistNAMES".

               The CvDEPTH'th entry of a PADLIST is a PAD (an AV) which is the stack frame at
               that depth of recursion into the CV.  The 0th slot of a frame AV is an AV which is
               @_.  Other entries are storage for variables and op targets.

               Iterating over the PADNAMELIST iterates over all possible pad items.  Pad slots
               for targets ("SVs_PADTMP") and GVs end up having &PL_padname_undef "names", while
               slots for constants have &PL_padname_const "names" (see "pad_alloc").  That
               &PL_padname_undef and &PL_padname_const are used is an implementation detail
               subject to change.  To test for them, use "!PadnamePV(name)" and
               "PadnamePV(name) && !PadnameLEN(name)", respectively.

               Only "my"/"our" variable slots get valid names.  The rest are op
               targets/GVs/constants which are statically allocated or resolved at compile time.
               These don't have names by which they can be looked up from Perl code at run time
               through eval"" the way "my"/"our" variables can be.  Since they can't be looked up
               by "name" but only by their index allocated at compile time (which is usually in
               "PL_op-"op_targ>), wasting a name SV for them doesn't make sense.

               The pad names in the PADNAMELIST have their PV holding the name of the variable.
               The "COP_SEQ_RANGE_LOW" and "_HIGH" fields form a range (low+1..high inclusive) of
               cop_seq numbers for which the name is valid.  During compilation, these fields may
               hold the special value PERL_PADSEQ_INTRO to indicate various stages:

                COP_SEQ_RANGE_LOW        _HIGH
                -----------------        -----
                PERL_PADSEQ_INTRO            0   variable not yet introduced:
                                                 { my ($x
                valid-seq#   PERL_PADSEQ_INTRO   variable in scope:
                                                 { my ($x);
                valid-seq#          valid-seq#   compilation of scope complete:
                                                 { my ($x); .... }

               When a lexical var hasn't yet been introduced, it already exists from the
               perspective of duplicate declarations, but not for variable lookups, e.g.

                   my ($x, $x); # '"my" variable $x masks earlier declaration'
                   my $x = $x;  # equal to my $x = $::x;

               For typed lexicals "PadnameTYPE" points at the type stash.  For "our" lexicals,
               "PadnameOURSTASH" points at the stash of the associated global (so that duplicate
               "our" declarations in the same package can be detected).  "PadnameGEN" is
               sometimes used to store the generation number during compilation.

               If "PadnameOUTER" is set on the pad name, then that slot in the frame AV is a
               REFCNT'ed reference to a lexical from "outside".  Such entries are sometimes
               referred to as 'fake'.  In this case, the name does not use 'low' and 'high' to
               store a cop_seq range, since it is in scope throughout.  Instead 'high' stores
               some flags containing info about the real lexical (is it declared in an anon, and
               is it capable of being instantiated multiple times?), and for fake ANONs, 'low'
               contains the index within the parent's pad where the lexical's value is stored, to
               make cloning quicker.

               If the 'name' is "&" the corresponding entry in the PAD is a CV representing a
               possible closure.

               Note that formats are treated as anon subs, and are cloned each time write is
               called (if necessary).

               The flag "SVs_PADSTALE" is cleared on lexicals each time the "my()" is executed,
               and set on scope exit.  This allows the "Variable $x is not available" warning to
               be generated in evals, such as

                   { my $x = 1; sub f { eval '$x'} } f();

               For state vars, "SVs_PADSTALE" is overloaded to mean 'not yet initialised', but
               this internal state is stored in a separate pad entry.

                       PADLIST * CvPADLIST(CV *cv)

       pad_add_name_pvs
               Exactly like "pad_add_name_pvn", but takes a "NUL"-terminated literal string
               instead of a string/length pair.

                       PADOFFSET pad_add_name_pvs(const char *name, U32 flags,
                                                  HV *typestash, HV *ourstash)

       PadARRAY
               NOTE: this function is experimental and may change or be removed without notice.

               The C array of pad entries.

                       SV **   PadARRAY(PAD pad)

       pad_findmy_pvs
               Exactly like "pad_findmy_pvn", but takes a "NUL"-terminated literal string instead
               of a string/length pair.

                       PADOFFSET pad_findmy_pvs(const char *name, U32 flags)

       PadlistARRAY
               NOTE: this function is experimental and may change or be removed without notice.

               The C array of a padlist, containing the pads.  Only subscript it with numbers >=
               1, as the 0th entry is not guaranteed to remain usable.

                       PAD **  PadlistARRAY(PADLIST padlist)

       PadlistMAX
               NOTE: this function is experimental and may change or be removed without notice.

               The index of the last allocated space in the padlist.  Note that the last pad may
               be in an earlier slot.  Any entries following it will be "NULL" in that case.

                       SSize_t PadlistMAX(PADLIST padlist)

       PadlistNAMES
               NOTE: this function is experimental and may change or be removed without notice.

               The names associated with pad entries.

                       PADNAMELIST * PadlistNAMES(PADLIST padlist)

       PadlistNAMESARRAY
               NOTE: this function is experimental and may change or be removed without notice.

               The C array of pad names.

                       PADNAME ** PadlistNAMESARRAY(PADLIST padlist)

       PadlistNAMESMAX
               NOTE: this function is experimental and may change or be removed without notice.

               The index of the last pad name.

                       SSize_t PadlistNAMESMAX(PADLIST padlist)

       PadlistREFCNT
               NOTE: this function is experimental and may change or be removed without notice.

               The reference count of the padlist.  Currently this is always 1.

                       U32     PadlistREFCNT(PADLIST padlist)

       PadMAX  NOTE: this function is experimental and may change or be removed without notice.

               The index of the last pad entry.

                       SSize_t PadMAX(PAD pad)

       PadnameLEN
               NOTE: this function is experimental and may change or be removed without notice.

               The length of the name.

                       STRLEN  PadnameLEN(PADNAME pn)

       PadnamelistARRAY
               NOTE: this function is experimental and may change or be removed without notice.

               The C array of pad names.

                       PADNAME ** PadnamelistARRAY(PADNAMELIST pnl)

       PadnamelistMAX
               NOTE: this function is experimental and may change or be removed without notice.

               The index of the last pad name.

                       SSize_t PadnamelistMAX(PADNAMELIST pnl)

       PadnamelistREFCNT
               NOTE: this function is experimental and may change or be removed without notice.

               The reference count of the pad name list.

                       SSize_t PadnamelistREFCNT(PADNAMELIST pnl)

       PadnamelistREFCNT_dec
               NOTE: this function is experimental and may change or be removed without notice.

               Lowers the reference count of the pad name list.

                       void    PadnamelistREFCNT_dec(PADNAMELIST pnl)

       PadnamePV
               NOTE: this function is experimental and may change or be removed without notice.

               The name stored in the pad name struct.  This returns "NULL" for a target slot.

                       char *  PadnamePV(PADNAME pn)

       PadnameREFCNT
               NOTE: this function is experimental and may change or be removed without notice.

               The reference count of the pad name.

                       SSize_t PadnameREFCNT(PADNAME pn)

       PadnameREFCNT_dec
               NOTE: this function is experimental and may change or be removed without notice.

               Lowers the reference count of the pad name.

                       void    PadnameREFCNT_dec(PADNAME pn)

       PadnameSV
               NOTE: this function is experimental and may change or be removed without notice.

               Returns the pad name as a mortal SV.

                       SV *    PadnameSV(PADNAME pn)

       PadnameUTF8
               NOTE: this function is experimental and may change or be removed without notice.

               Whether PadnamePV is in UTF-8.  Currently, this is always true.

                       bool    PadnameUTF8(PADNAME pn)

       pad_new Create a new padlist, updating the global variables for the currently-compiling
               padlist to point to the new padlist.  The following flags can be OR'ed together:

                   padnew_CLONE        this pad is for a cloned CV
                   padnew_SAVE         save old globals on the save stack
                   padnew_SAVESUB      also save extra stuff for start of sub

                       PADLIST * pad_new(int flags)

       PL_comppad
               NOTE: this function is experimental and may change or be removed without notice.

               During compilation, this points to the array containing the values part of the pad
               for the currently-compiling code.  (At runtime a CV may have many such value
               arrays; at compile time just one is constructed.)  At runtime, this points to the
               array containing the currently-relevant values for the pad for the currently-
               executing code.

       PL_comppad_name
               NOTE: this function is experimental and may change or be removed without notice.

               During compilation, this points to the array containing the names part of the pad
               for the currently-compiling code.

       PL_curpad
               NOTE: this function is experimental and may change or be removed without notice.

               Points directly to the body of the "PL_comppad" array.  (I.e., this is
               "PAD_ARRAY(PL_comppad)".)

Per-Interpreter Variables

       PL_modglobal
               "PL_modglobal" is a general purpose, interpreter global HV for use by extensions
               that need to keep information on a per-interpreter basis.  In a pinch, it can also
               be used as a symbol table for extensions to share data among each other.  It is a
               good idea to use keys prefixed by the package name of the extension that owns the
               data.

                       HV*     PL_modglobal

       PL_na   A convenience variable which is typically used with "SvPV" when one doesn't care
               about the length of the string.  It is usually more efficient to either declare a
               local variable and use that instead or to use the "SvPV_nolen" macro.

                       STRLEN  PL_na

       PL_opfreehook
               When non-"NULL", the function pointed by this variable will be called each time an
               OP is freed with the corresponding OP as the argument.  This allows extensions to
               free any extra attribute they have locally attached to an OP.  It is also assured
               to first fire for the parent OP and then for its kids.

               When you replace this variable, it is considered a good practice to store the
               possibly previously installed hook and that you recall it inside your own.

                       Perl_ophook_t   PL_opfreehook

       PL_peepp
               Pointer to the per-subroutine peephole optimiser.  This is a function that gets
               called at the end of compilation of a Perl subroutine (or equivalently independent
               piece of Perl code) to perform fixups of some ops and to perform small-scale
               optimisations.  The function is called once for each subroutine that is compiled,
               and is passed, as sole parameter, a pointer to the op that is the entry point to
               the subroutine.  It modifies the op tree in place.

               The peephole optimiser should never be completely replaced.  Rather, add code to
               it by wrapping the existing optimiser.  The basic way to do this can be seen in
               "Compile pass 3: peephole optimization" in perlguts.  If the new code wishes to
               operate on ops throughout the subroutine's structure, rather than just at the top
               level, it is likely to be more convenient to wrap the "PL_rpeepp" hook.

                       peep_t  PL_peepp

       PL_rpeepp
               Pointer to the recursive peephole optimiser.  This is a function that gets called
               at the end of compilation of a Perl subroutine (or equivalently independent piece
               of Perl code) to perform fixups of some ops and to perform small-scale
               optimisations.  The function is called once for each chain of ops linked through
               their "op_next" fields; it is recursively called to handle each side chain.  It is
               passed, as sole parameter, a pointer to the op that is at the head of the chain.
               It modifies the op tree in place.

               The peephole optimiser should never be completely replaced.  Rather, add code to
               it by wrapping the existing optimiser.  The basic way to do this can be seen in
               "Compile pass 3: peephole optimization" in perlguts.  If the new code wishes to
               operate only on ops at a subroutine's top level, rather than throughout the
               structure, it is likely to be more convenient to wrap the "PL_peepp" hook.

                       peep_t  PL_rpeepp

       PL_sv_no
               This is the "false" SV.  See "PL_sv_yes".  Always refer to this as &PL_sv_no.

                       SV      PL_sv_no

       PL_sv_undef
               This is the "undef" SV.  Always refer to this as &PL_sv_undef.

                       SV      PL_sv_undef

       PL_sv_yes
               This is the "true" SV.  See "PL_sv_no".  Always refer to this as &PL_sv_yes.

                       SV      PL_sv_yes

REGEXP Functions

       SvRX    Convenience macro to get the REGEXP from a SV.  This is approximately equivalent
               to the following snippet:

                   if (SvMAGICAL(sv))
                       mg_get(sv);
                   if (SvROK(sv))
                       sv = MUTABLE_SV(SvRV(sv));
                   if (SvTYPE(sv) == SVt_REGEXP)
                       return (REGEXP*) sv;

               "NULL" will be returned if a REGEXP* is not found.

                       REGEXP * SvRX(SV *sv)

       SvRXOK  Returns a boolean indicating whether the SV (or the one it references) is a
               REGEXP.

               If you want to do something with the REGEXP* later use SvRX instead and check for
               NULL.

                       bool    SvRXOK(SV* sv)

Stack Manipulation Macros

       dMARK   Declare a stack marker variable, "mark", for the XSUB.  See "MARK" and
               "dORIGMARK".

                               dMARK;

       dORIGMARK
               Saves the original stack mark for the XSUB.  See "ORIGMARK".

                               dORIGMARK;

       dSP     Declares a local copy of perl's stack pointer for the XSUB, available via the "SP"
               macro.  See "SP".

                               dSP;

       EXTEND  Used to extend the argument stack for an XSUB's return values.  Once used,
               guarantees that there is room for at least "nitems" to be pushed onto the stack.

                       void    EXTEND(SP, SSize_t nitems)

       MARK    Stack marker variable for the XSUB.  See "dMARK".

       mPUSHi  Push an integer onto the stack.  The stack must have room for this element.  Does
               not use "TARG".  See also "PUSHi", "mXPUSHi" and "XPUSHi".

                       void    mPUSHi(IV iv)

       mPUSHn  Push a double onto the stack.  The stack must have room for this element.  Does
               not use "TARG".  See also "PUSHn", "mXPUSHn" and "XPUSHn".

                       void    mPUSHn(NV nv)

       mPUSHp  Push a string onto the stack.  The stack must have room for this element.  The
               "len" indicates the length of the string.  Does not use "TARG".  See also "PUSHp",
               "mXPUSHp" and "XPUSHp".

                       void    mPUSHp(char* str, STRLEN len)

       mPUSHs  Push an SV onto the stack and mortalizes the SV.  The stack must have room for
               this element.  Does not use "TARG".  See also "PUSHs" and "mXPUSHs".

                       void    mPUSHs(SV* sv)

       mPUSHu  Push an unsigned integer onto the stack.  The stack must have room for this
               element.  Does not use "TARG".  See also "PUSHu", "mXPUSHu" and "XPUSHu".

                       void    mPUSHu(UV uv)

       mXPUSHi Push an integer onto the stack, extending the stack if necessary.  Does not use
               "TARG".  See also "XPUSHi", "mPUSHi" and "PUSHi".

                       void    mXPUSHi(IV iv)

       mXPUSHn Push a double onto the stack, extending the stack if necessary.  Does not use
               "TARG".  See also "XPUSHn", "mPUSHn" and "PUSHn".

                       void    mXPUSHn(NV nv)

       mXPUSHp Push a string onto the stack, extending the stack if necessary.  The "len"
               indicates the length of the string.  Does not use "TARG".  See also "XPUSHp",
               "mPUSHp" and "PUSHp".

                       void    mXPUSHp(char* str, STRLEN len)

       mXPUSHs Push an SV onto the stack, extending the stack if necessary and mortalizes the SV.
               Does not use "TARG".  See also "XPUSHs" and "mPUSHs".

                       void    mXPUSHs(SV* sv)

       mXPUSHu Push an unsigned integer onto the stack, extending the stack if necessary.  Does
               not use "TARG".  See also "XPUSHu", "mPUSHu" and "PUSHu".

                       void    mXPUSHu(UV uv)

       ORIGMARK
               The original stack mark for the XSUB.  See "dORIGMARK".

       POPi    Pops an integer off the stack.

                       IV      POPi

       POPl    Pops a long off the stack.

                       long    POPl

       POPn    Pops a double off the stack.

                       NV      POPn

       POPp    Pops a string off the stack.

                       char*   POPp

       POPpbytex
               Pops a string off the stack which must consist of bytes i.e. characters < 256.

                       char*   POPpbytex

       POPpx   Pops a string off the stack.  Identical to POPp.  There are two names for
               historical reasons.

                       char*   POPpx

       POPs    Pops an SV off the stack.

                       SV*     POPs

       POPu    Pops an unsigned integer off the stack.

                       UV      POPu

       POPul   Pops an unsigned long off the stack.

                       long    POPul

       PUSHi   Push an integer onto the stack.  The stack must have room for this element.
               Handles 'set' magic.  Uses "TARG", so "dTARGET" or "dXSTARG" should be called to
               declare it.  Do not call multiple "TARG"-oriented macros to return lists from
               XSUB's - see "mPUSHi" instead.  See also "XPUSHi" and "mXPUSHi".

                       void    PUSHi(IV iv)

       PUSHMARK
               Opening bracket for arguments on a callback.  See "PUTBACK" and perlcall.

                       void    PUSHMARK(SP)

       PUSHmortal
               Push a new mortal SV onto the stack.  The stack must have room for this element.
               Does not use "TARG".  See also "PUSHs", "XPUSHmortal" and "XPUSHs".

                       void    PUSHmortal()

       PUSHn   Push a double onto the stack.  The stack must have room for this element.  Handles
               'set' magic.  Uses "TARG", so "dTARGET" or "dXSTARG" should be called to declare
               it.  Do not call multiple "TARG"-oriented macros to return lists from XSUB's - see
               "mPUSHn" instead.  See also "XPUSHn" and "mXPUSHn".

                       void    PUSHn(NV nv)

       PUSHp   Push a string onto the stack.  The stack must have room for this element.  The
               "len" indicates the length of the string.  Handles 'set' magic.  Uses "TARG", so
               "dTARGET" or "dXSTARG" should be called to declare it.  Do not call multiple
               "TARG"-oriented macros to return lists from XSUB's - see "mPUSHp" instead.  See
               also "XPUSHp" and "mXPUSHp".

                       void    PUSHp(char* str, STRLEN len)

       PUSHs   Push an SV onto the stack.  The stack must have room for this element.  Does not
               handle 'set' magic.  Does not use "TARG".  See also "PUSHmortal", "XPUSHs", and
               "XPUSHmortal".

                       void    PUSHs(SV* sv)

       PUSHu   Push an unsigned integer onto the stack.  The stack must have room for this
               element.  Handles 'set' magic.  Uses "TARG", so "dTARGET" or "dXSTARG" should be
               called to declare it.  Do not call multiple "TARG"-oriented macros to return lists
               from XSUB's - see "mPUSHu" instead.  See also "XPUSHu" and "mXPUSHu".

                       void    PUSHu(UV uv)

       PUTBACK Closing bracket for XSUB arguments.  This is usually handled by "xsubpp".  See
               "PUSHMARK" and perlcall for other uses.

                               PUTBACK;

       SP      Stack pointer.  This is usually handled by "xsubpp".  See "dSP" and "SPAGAIN".

       SPAGAIN Refetch the stack pointer.  Used after a callback.  See perlcall.

                               SPAGAIN;

       XPUSHi  Push an integer onto the stack, extending the stack if necessary.  Handles 'set'
               magic.  Uses "TARG", so "dTARGET" or "dXSTARG" should be called to declare it.  Do
               not call multiple "TARG"-oriented macros to return lists from XSUB's - see
               "mXPUSHi" instead.  See also "PUSHi" and "mPUSHi".

                       void    XPUSHi(IV iv)

       XPUSHmortal
               Push a new mortal SV onto the stack, extending the stack if necessary.  Does not
               use "TARG".  See also "XPUSHs", "PUSHmortal" and "PUSHs".

                       void    XPUSHmortal()

       XPUSHn  Push a double onto the stack, extending the stack if necessary.  Handles 'set'
               magic.  Uses "TARG", so "dTARGET" or "dXSTARG" should be called to declare it.  Do
               not call multiple "TARG"-oriented macros to return lists from XSUB's - see
               "mXPUSHn" instead.  See also "PUSHn" and "mPUSHn".

                       void    XPUSHn(NV nv)

       XPUSHp  Push a string onto the stack, extending the stack if necessary.  The "len"
               indicates the length of the string.  Handles 'set' magic.  Uses "TARG", so
               "dTARGET" or "dXSTARG" should be called to declare it.  Do not call multiple
               "TARG"-oriented macros to return lists from XSUB's - see "mXPUSHp" instead.  See
               also "PUSHp" and "mPUSHp".

                       void    XPUSHp(char* str, STRLEN len)

       XPUSHs  Push an SV onto the stack, extending the stack if necessary.  Does not handle
               'set' magic.  Does not use "TARG".  See also "XPUSHmortal", "PUSHs" and
               "PUSHmortal".

                       void    XPUSHs(SV* sv)

       XPUSHu  Push an unsigned integer onto the stack, extending the stack if necessary.
               Handles 'set' magic.  Uses "TARG", so "dTARGET" or "dXSTARG" should be called to
               declare it.  Do not call multiple "TARG"-oriented macros to return lists from
               XSUB's - see "mXPUSHu" instead.  See also "PUSHu" and "mPUSHu".

                       void    XPUSHu(UV uv)

       XSRETURN
               Return from XSUB, indicating number of items on the stack.  This is usually
               handled by "xsubpp".

                       void    XSRETURN(int nitems)

       XSRETURN_EMPTY
               Return an empty list from an XSUB immediately.

                               XSRETURN_EMPTY;

       XSRETURN_IV
               Return an integer from an XSUB immediately.  Uses "XST_mIV".

                       void    XSRETURN_IV(IV iv)

       XSRETURN_NO
               Return &PL_sv_no from an XSUB immediately.  Uses "XST_mNO".

                               XSRETURN_NO;

       XSRETURN_NV
               Return a double from an XSUB immediately.  Uses "XST_mNV".

                       void    XSRETURN_NV(NV nv)

       XSRETURN_PV
               Return a copy of a string from an XSUB immediately.  Uses "XST_mPV".

                       void    XSRETURN_PV(char* str)

       XSRETURN_UNDEF
               Return &PL_sv_undef from an XSUB immediately.  Uses "XST_mUNDEF".

                               XSRETURN_UNDEF;

       XSRETURN_UV
               Return an integer from an XSUB immediately.  Uses "XST_mUV".

                       void    XSRETURN_UV(IV uv)

       XSRETURN_YES
               Return &PL_sv_yes from an XSUB immediately.  Uses "XST_mYES".

                               XSRETURN_YES;

       XST_mIV Place an integer into the specified position "pos" on the stack.  The value is
               stored in a new mortal SV.

                       void    XST_mIV(int pos, IV iv)

       XST_mNO Place &PL_sv_no into the specified position "pos" on the stack.

                       void    XST_mNO(int pos)

       XST_mNV Place a double into the specified position "pos" on the stack.  The value is
               stored in a new mortal SV.

                       void    XST_mNV(int pos, NV nv)

       XST_mPV Place a copy of a string into the specified position "pos" on the stack.  The
               value is stored in a new mortal SV.

                       void    XST_mPV(int pos, char* str)

       XST_mUNDEF
               Place &PL_sv_undef into the specified position "pos" on the stack.

                       void    XST_mUNDEF(int pos)

       XST_mYES
               Place &PL_sv_yes into the specified position "pos" on the stack.

                       void    XST_mYES(int pos)

SV-Body Allocation

       looks_like_number
               Test if the content of an SV looks like a number (or is a number).  "Inf" and
               "Infinity" are treated as numbers (so will not issue a non-numeric warning), even
               if your "atof()" doesn't grok them.  Get-magic is ignored.

                       I32     looks_like_number(SV *const sv)

       newRV_noinc
               Creates an RV wrapper for an SV.  The reference count for the original SV is not
               incremented.

                       SV*     newRV_noinc(SV *const tmpRef)

       newSV   Creates a new SV.  A non-zero "len" parameter indicates the number of bytes of
               preallocated string space the SV should have.  An extra byte for a trailing "NUL"
               is also reserved.  ("SvPOK" is not set for the SV even if string space is
               allocated.)  The reference count for the new SV is set to 1.

               In 5.9.3, "newSV()" replaces the older "NEWSV()" API, and drops the first
               parameter, x, a debug aid which allowed callers to identify themselves.  This aid
               has been superseded by a new build option, "PERL_MEM_LOG" (see "PERL_MEM_LOG" in
               perlhacktips).  The older API is still there for use in XS modules supporting
               older perls.

                       SV*     newSV(const STRLEN len)

       newSVhek
               Creates a new SV from the hash key structure.  It will generate scalars that point
               to the shared string table where possible.  Returns a new (undefined) SV if "hek"
               is NULL.

                       SV*     newSVhek(const HEK *const hek)

       newSViv Creates a new SV and copies an integer into it.  The reference count for the SV is
               set to 1.

                       SV*     newSViv(const IV i)

       newSVnv Creates a new SV and copies a floating point value into it.  The reference count
               for the SV is set to 1.

                       SV*     newSVnv(const NV n)

       newSVpv Creates a new SV and copies a string (which may contain "NUL" ("\0") characters)
               into it.  The reference count for the SV is set to 1.  If "len" is zero, Perl will
               compute the length using "strlen()", (which means if you use this option, that "s"
               can't have embedded "NUL" characters and has to have a terminating "NUL" byte).

               This function can cause reliability issues if you are likely to pass in empty
               strings that are not null terminated, because it will run strlen on the string and
               potentially run past valid memory.

               Using "newSVpvn" is a safer alternative for non "NUL" terminated strings.  For
               string literals use "newSVpvs" instead.  This function will work fine for "NUL"
               terminated strings, but if you want to avoid the if statement on whether to call
               "strlen" use "newSVpvn" instead (calling "strlen" yourself).

                       SV*     newSVpv(const char *const s, const STRLEN len)

       newSVpvf
               Creates a new SV and initializes it with the string formatted like "sv_catpvf".

                       SV*     newSVpvf(const char *const pat, ...)

       newSVpvn
               Creates a new SV and copies a string into it, which may contain "NUL" characters
               ("\0") and other binary data.  The reference count for the SV is set to 1.  Note
               that if "len" is zero, Perl will create a zero length (Perl) string.  You are
               responsible for ensuring that the source buffer is at least "len" bytes long.  If
               the "buffer" argument is NULL the new SV will be undefined.

                       SV*     newSVpvn(const char *const s, const STRLEN len)

       newSVpvn_flags
               Creates a new SV and copies a string (which may contain "NUL" ("\0") characters)
               into it.  The reference count for the SV is set to 1.  Note that if "len" is zero,
               Perl will create a zero length string.  You are responsible for ensuring that the
               source string is at least "len" bytes long.  If the "s" argument is NULL the new
               SV will be undefined.  Currently the only flag bits accepted are "SVf_UTF8" and
               "SVs_TEMP".  If "SVs_TEMP" is set, then "sv_2mortal()" is called on the result
               before returning.  If "SVf_UTF8" is set, "s" is considered to be in UTF-8 and the
               "SVf_UTF8" flag will be set on the new SV.  "newSVpvn_utf8()" is a convenience
               wrapper for this function, defined as

                   #define newSVpvn_utf8(s, len, u)                    \
                       newSVpvn_flags((s), (len), (u) ? SVf_UTF8 : 0)

                       SV*     newSVpvn_flags(const char *const s,
                                              const STRLEN len,
                                              const U32 flags)

       newSVpvn_share
               Creates a new SV with its "SvPVX_const" pointing to a shared string in the string
               table.  If the string does not already exist in the table, it is created first.
               Turns on the "SvIsCOW" flag (or "READONLY" and "FAKE" in 5.16 and earlier).  If
               the "hash" parameter is non-zero, that value is used; otherwise the hash is
               computed.  The string's hash can later be retrieved from the SV with the
               "SvSHARED_HASH()" macro.  The idea here is that as the string table is used for
               shared hash keys these strings will have "SvPVX_const == HeKEY" and hash lookup
               will avoid string compare.

                       SV*     newSVpvn_share(const char* s, I32 len, U32 hash)

       newSVpvs
               Like "newSVpvn", but takes a "NUL"-terminated literal string instead of a
               string/length pair.

                       SV*     newSVpvs(const char* s)

       newSVpvs_flags
               Like "newSVpvn_flags", but takes a "NUL"-terminated literal string instead of a
               string/length pair.

                       SV*     newSVpvs_flags(const char* s, U32 flags)

       newSVpv_share
               Like "newSVpvn_share", but takes a "NUL"-terminated string instead of a
               string/length pair.

                       SV*     newSVpv_share(const char* s, U32 hash)

       newSVpvs_share
               Like "newSVpvn_share", but takes a "NUL"-terminated literal string instead of a
               string/length pair and omits the hash parameter.

                       SV*     newSVpvs_share(const char* s)

       newSVrv Creates a new SV for the existing RV, "rv", to point to.  If "rv" is not an RV
               then it will be upgraded to one.  If "classname" is non-null then the new SV will
               be blessed in the specified package.  The new SV is returned and its reference
               count is 1.  The reference count 1 is owned by "rv".

                       SV*     newSVrv(SV *const rv,
                                       const char *const classname)

       newSVsv Creates a new SV which is an exact duplicate of the original SV.  (Uses
               "sv_setsv".)

                       SV*     newSVsv(SV *const old)

       newSV_type
               Creates a new SV, of the type specified.  The reference count for the new SV is
               set to 1.

                       SV*     newSV_type(const svtype type)

       newSVuv Creates a new SV and copies an unsigned integer into it.  The reference count for
               the SV is set to 1.

                       SV*     newSVuv(const UV u)

       sv_2bool
               This macro is only used by "sv_true()" or its macro equivalent, and only if the
               latter's argument is neither "SvPOK", "SvIOK" nor "SvNOK".  It calls
               "sv_2bool_flags" with the "SV_GMAGIC" flag.

                       bool    sv_2bool(SV *const sv)

       sv_2bool_flags
               This function is only used by "sv_true()" and friends,  and only if the latter's
               argument is neither "SvPOK", "SvIOK" nor "SvNOK".  If the flags contain
               "SV_GMAGIC", then it does an "mg_get()" first.

                       bool    sv_2bool_flags(SV *sv, I32 flags)

       sv_2cv  Using various gambits, try to get a CV from an SV; in addition, try if possible to
               set *st and *gvp to the stash and GV associated with it.  The flags in "lref" are
               passed to "gv_fetchsv".

                       CV*     sv_2cv(SV* sv, HV **const st, GV **const gvp,
                                      const I32 lref)

       sv_2io  Using various gambits, try to get an IO from an SV: the IO slot if its a GV; or
               the recursive result if we're an RV; or the IO slot of the symbol named after the
               PV if we're a string.

               'Get' magic is ignored on the "sv" passed in, but will be called on "SvRV(sv)" if
               "sv" is an RV.

                       IO*     sv_2io(SV *const sv)

       sv_2iv_flags
               Return the integer value of an SV, doing any necessary string conversion.  If
               "flags" has the "SV_GMAGIC" bit set, does an "mg_get()" first.  Normally used via
               the "SvIV(sv)" and "SvIVx(sv)" macros.

                       IV      sv_2iv_flags(SV *const sv, const I32 flags)

       sv_2mortal
               Marks an existing SV as mortal.  The SV will be destroyed "soon", either by an
               explicit call to "FREETMPS", or by an implicit call at places such as statement
               boundaries.  "SvTEMP()" is turned on which means that the SV's string buffer can
               be "stolen" if this SV is copied.  See also "sv_newmortal" and "sv_mortalcopy".

                       SV*     sv_2mortal(SV *const sv)

       sv_2nv_flags
               Return the num value of an SV, doing any necessary string or integer conversion.
               If "flags" has the "SV_GMAGIC" bit set, does an "mg_get()" first.  Normally used
               via the "SvNV(sv)" and "SvNVx(sv)" macros.

                       NV      sv_2nv_flags(SV *const sv, const I32 flags)

       sv_2pvbyte
               Return a pointer to the byte-encoded representation of the SV, and set *lp to its
               length.  May cause the SV to be downgraded from UTF-8 as a side-effect.

               Usually accessed via the "SvPVbyte" macro.

                       char*   sv_2pvbyte(SV *sv, STRLEN *const lp)

       sv_2pvutf8
               Return a pointer to the UTF-8-encoded representation of the SV, and set *lp to its
               length.  May cause the SV to be upgraded to UTF-8 as a side-effect.

               Usually accessed via the "SvPVutf8" macro.

                       char*   sv_2pvutf8(SV *sv, STRLEN *const lp)

       sv_2pv_flags
               Returns a pointer to the string value of an SV, and sets *lp to its length.  If
               flags has the "SV_GMAGIC" bit set, does an "mg_get()" first.  Coerces "sv" to a
               string if necessary.  Normally invoked via the "SvPV_flags" macro.  "sv_2pv()" and
               "sv_2pv_nomg" usually end up here too.

                       char*   sv_2pv_flags(SV *const sv, STRLEN *const lp,
                                            const I32 flags)

       sv_2uv_flags
               Return the unsigned integer value of an SV, doing any necessary string conversion.
               If "flags" has the "SV_GMAGIC" bit set, does an "mg_get()" first.  Normally used
               via the "SvUV(sv)" and "SvUVx(sv)" macros.

                       UV      sv_2uv_flags(SV *const sv, const I32 flags)

       sv_backoff
               Remove any string offset.  You should normally use the "SvOOK_off" macro wrapper
               instead.

                       void    sv_backoff(SV *const sv)

       sv_bless
               Blesses an SV into a specified package.  The SV must be an RV.  The package must
               be designated by its stash (see "gv_stashpv").  The reference count of the SV is
               unaffected.

                       SV*     sv_bless(SV *const sv, HV *const stash)

       sv_catpv
               Concatenates the "NUL"-terminated string onto the end of the string which is in
               the SV.  If the SV has the UTF-8 status set, then the bytes appended should be
               valid UTF-8.  Handles 'get' magic, but not 'set' magic.  See "sv_catpv_mg".

                       void    sv_catpv(SV *const sv, const char* ptr)

       sv_catpvf
               Processes its arguments like "sv_catpvfn", and appends the formatted output to an
               SV.  As with "sv_catpvfn" called with a non-null C-style variable argument list,
               argument reordering is not supported.  If the appended data contains "wide"
               characters (including, but not limited to, SVs with a UTF-8 PV formatted with %s,
               and characters >255 formatted with %c), the original SV might get upgraded to
               UTF-8.  Handles 'get' magic, but not 'set' magic.  See "sv_catpvf_mg".  If the
               original SV was UTF-8, the pattern should be valid UTF-8; if the original SV was
               bytes, the pattern should be too.

                       void    sv_catpvf(SV *const sv, const char *const pat,
                                         ...)

       sv_catpvf_mg
               Like "sv_catpvf", but also handles 'set' magic.

                       void    sv_catpvf_mg(SV *const sv,
                                            const char *const pat, ...)

       sv_catpvn
               Concatenates the string onto the end of the string which is in the SV.  "len"
               indicates number of bytes to copy.  If the SV has the UTF-8 status set, then the
               bytes appended should be valid UTF-8.  Handles 'get' magic, but not 'set' magic.
               See "sv_catpvn_mg".

                       void    sv_catpvn(SV *dsv, const char *sstr, STRLEN len)

       sv_catpvn_flags
               Concatenates the string onto the end of the string which is in the SV.  The "len"
               indicates number of bytes to copy.

               By default, the string appended is assumed to be valid UTF-8 if the SV has the
               UTF-8 status set, and a string of bytes otherwise.  One can force the appended
               string to be interpreted as UTF-8 by supplying the "SV_CATUTF8" flag, and as bytes
               by supplying the "SV_CATBYTES" flag; the SV or the string appended will be
               upgraded to UTF-8 if necessary.

               If "flags" has the "SV_SMAGIC" bit set, will "mg_set" on "dsv" afterwards if
               appropriate.  "sv_catpvn" and "sv_catpvn_nomg" are implemented in terms of this
               function.

                       void    sv_catpvn_flags(SV *const dstr,
                                               const char *sstr,
                                               const STRLEN len,
                                               const I32 flags)

       sv_catpvs
               Like "sv_catpvn", but takes a "NUL"-terminated literal string instead of a
               string/length pair.

                       void    sv_catpvs(SV* sv, const char* s)

       sv_catpvs_flags
               Like "sv_catpvn_flags", but takes a "NUL"-terminated literal string instead of a
               string/length pair.

                       void    sv_catpvs_flags(SV* sv, const char* s,
                                               I32 flags)

       sv_catpvs_mg
               Like "sv_catpvn_mg", but takes a "NUL"-terminated literal string instead of a
               string/length pair.

                       void    sv_catpvs_mg(SV* sv, const char* s)

       sv_catpvs_nomg
               Like "sv_catpvn_nomg", but takes a "NUL"-terminated literal string instead of a
               string/length pair.

                       void    sv_catpvs_nomg(SV* sv, const char* s)

       sv_catpv_flags
               Concatenates the "NUL"-terminated string onto the end of the string which is in
               the SV.  If the SV has the UTF-8 status set, then the bytes appended should be
               valid UTF-8.  If "flags" has the "SV_SMAGIC" bit set, will "mg_set" on the
               modified SV if appropriate.

                       void    sv_catpv_flags(SV *dstr, const char *sstr,
                                              const I32 flags)

       sv_catpv_mg
               Like "sv_catpv", but also handles 'set' magic.

                       void    sv_catpv_mg(SV *const sv, const char *const ptr)

       sv_catsv
               Concatenates the string from SV "ssv" onto the end of the string in SV "dsv".  If
               "ssv" is null, does nothing; otherwise modifies only "dsv".  Handles 'get' magic
               on both SVs, but no 'set' magic.  See "sv_catsv_mg" and "sv_catsv_nomg".

                       void    sv_catsv(SV *dstr, SV *sstr)

       sv_catsv_flags
               Concatenates the string from SV "ssv" onto the end of the string in SV "dsv".  If
               "ssv" is null, does nothing; otherwise modifies only "dsv".  If "flags" has the
               "SV_GMAGIC" bit set, will call "mg_get" on both SVs if appropriate.  If "flags"
               has the "SV_SMAGIC" bit set, "mg_set" will be called on the modified SV afterward,
               if appropriate.  "sv_catsv", "sv_catsv_nomg", and "sv_catsv_mg" are implemented in
               terms of this function.

                       void    sv_catsv_flags(SV *const dsv, SV *const ssv,
                                              const I32 flags)

       sv_chop Efficient removal of characters from the beginning of the string buffer.
               "SvPOK(sv)", or at least "SvPOKp(sv)", must be true and "ptr" must be a pointer to
               somewhere inside the string buffer.  "ptr" becomes the first character of the
               adjusted string.  Uses the "OOK" hack.  On return, only "SvPOK(sv)" and
               "SvPOKp(sv)" among the "OK" flags will be true.

               Beware: after this function returns, "ptr" and SvPVX_const(sv) may no longer refer
               to the same chunk of data.

               The unfortunate similarity of this function's name to that of Perl's "chop"
               operator is strictly coincidental.  This function works from the left; "chop"
               works from the right.

                       void    sv_chop(SV *const sv, const char *const ptr)

       sv_clear
               Clear an SV: call any destructors, free up any memory used by the body, and free
               the body itself.  The SV's head is not freed, although its type is set to all 1's
               so that it won't inadvertently be assumed to be live during global destruction
               etc.  This function should only be called when "REFCNT" is zero.  Most of the time
               you'll want to call "sv_free()" (or its macro wrapper "SvREFCNT_dec") instead.

                       void    sv_clear(SV *const orig_sv)

       sv_cmp  Compares the strings in two SVs.  Returns -1, 0, or 1 indicating whether the
               string in "sv1" is less than, equal to, or greater than the string in "sv2".  Is
               UTF-8 and 'use bytes' aware, handles get magic, and will coerce its args to
               strings if necessary.  See also "sv_cmp_locale".

                       I32     sv_cmp(SV *const sv1, SV *const sv2)

       sv_cmp_flags
               Compares the strings in two SVs.  Returns -1, 0, or 1 indicating whether the
               string in "sv1" is less than, equal to, or greater than the string in "sv2".  Is
               UTF-8 and 'use bytes' aware and will coerce its args to strings if necessary.  If
               the flags has the "SV_GMAGIC" bit set, it handles get magic.  See also
               "sv_cmp_locale_flags".

                       I32     sv_cmp_flags(SV *const sv1, SV *const sv2,
                                            const U32 flags)

       sv_cmp_locale
               Compares the strings in two SVs in a locale-aware manner.  Is UTF-8 and
               'use bytes' aware, handles get magic, and will coerce its args to strings if
               necessary.  See also "sv_cmp".

                       I32     sv_cmp_locale(SV *const sv1, SV *const sv2)

       sv_cmp_locale_flags
               Compares the strings in two SVs in a locale-aware manner.  Is UTF-8 and
               'use bytes' aware and will coerce its args to strings if necessary.  If the flags
               contain "SV_GMAGIC", it handles get magic.  See also "sv_cmp_flags".

                       I32     sv_cmp_locale_flags(SV *const sv1,
                                                   SV *const sv2,
                                                   const U32 flags)

       sv_collxfrm
               This calls "sv_collxfrm_flags" with the SV_GMAGIC flag.  See "sv_collxfrm_flags".

                       char*   sv_collxfrm(SV *const sv, STRLEN *const nxp)

       sv_collxfrm_flags
               Add Collate Transform magic to an SV if it doesn't already have it.  If the flags
               contain "SV_GMAGIC", it handles get-magic.

               Any scalar variable may carry "PERL_MAGIC_collxfrm" magic that contains the scalar
               data of the variable, but transformed to such a format that a normal memory
               comparison can be used to compare the data according to the locale settings.

                       char*   sv_collxfrm_flags(SV *const sv,
                                                 STRLEN *const nxp,
                                                 I32 const flags)

       sv_copypv
               Copies a stringified representation of the source SV into the destination SV.
               Automatically performs any necessary "mg_get" and coercion of numeric values into
               strings.  Guaranteed to preserve "UTF8" flag even from overloaded objects.
               Similar in nature to "sv_2pv[_flags]" but operates directly on an SV instead of
               just the string.  Mostly uses "sv_2pv_flags" to do its work, except when that
               would lose the UTF-8'ness of the PV.

                       void    sv_copypv(SV *const dsv, SV *const ssv)

       sv_copypv_flags
               Implementation of "sv_copypv" and "sv_copypv_nomg".  Calls get magic iff flags has
               the "SV_GMAGIC" bit set.

                       void    sv_copypv_flags(SV *const dsv, SV *const ssv,
                                               const I32 flags)

       sv_copypv_nomg
               Like "sv_copypv", but doesn't invoke get magic first.

                       void    sv_copypv_nomg(SV *const dsv, SV *const ssv)

       sv_dec  Auto-decrement of the value in the SV, doing string to numeric conversion if
               necessary.  Handles 'get' magic and operator overloading.

                       void    sv_dec(SV *const sv)

       sv_dec_nomg
               Auto-decrement of the value in the SV, doing string to numeric conversion if
               necessary.  Handles operator overloading.  Skips handling 'get' magic.

                       void    sv_dec_nomg(SV *const sv)

       sv_eq   Returns a boolean indicating whether the strings in the two SVs are identical.  Is
               UTF-8 and 'use bytes' aware, handles get magic, and will coerce its args to
               strings if necessary.

                       I32     sv_eq(SV* sv1, SV* sv2)

       sv_eq_flags
               Returns a boolean indicating whether the strings in the two SVs are identical.  Is
               UTF-8 and 'use bytes' aware and coerces its args to strings if necessary.  If the
               flags has the "SV_GMAGIC" bit set, it handles get-magic, too.

                       I32     sv_eq_flags(SV* sv1, SV* sv2, const U32 flags)

       sv_force_normal_flags
               Undo various types of fakery on an SV, where fakery means "more than" a string: if
               the PV is a shared string, make a private copy; if we're a ref, stop refing; if
               we're a glob, downgrade to an "xpvmg"; if we're a copy-on-write scalar, this is
               the on-write time when we do the copy, and is also used locally; if this is a
               vstring, drop the vstring magic.  If "SV_COW_DROP_PV" is set then a copy-on-write
               scalar drops its PV buffer (if any) and becomes "SvPOK_off" rather than making a
               copy.  (Used where this scalar is about to be set to some other value.)  In
               addition, the "flags" parameter gets passed to "sv_unref_flags()" when unreffing.
               "sv_force_normal" calls this function with flags set to 0.

               This function is expected to be used to signal to perl that this SV is about to be
               written to, and any extra book-keeping needs to be taken care of.  Hence, it
               croaks on read-only values.

                       void    sv_force_normal_flags(SV *const sv,
                                                     const U32 flags)

       sv_free Decrement an SV's reference count, and if it drops to zero, call "sv_clear" to
               invoke destructors and free up any memory used by the body; finally, deallocating
               the SV's head itself.  Normally called via a wrapper macro "SvREFCNT_dec".

                       void    sv_free(SV *const sv)

       sv_gets Get a line from the filehandle and store it into the SV, optionally appending to
               the currently-stored string.  If "append" is not 0, the line is appended to the SV
               instead of overwriting it.  "append" should be set to the byte offset that the
               appended string should start at in the SV (typically, "SvCUR(sv)" is a suitable
               choice).

                       char*   sv_gets(SV *const sv, PerlIO *const fp,
                                       I32 append)

       sv_get_backrefs
               NOTE: this function is experimental and may change or be removed without notice.

               If "sv" is the target of a weak reference then it returns the back references
               structure associated with the sv; otherwise return "NULL".

               When returning a non-null result the type of the return is relevant. If it is an
               AV then the elements of the AV are the weak reference RVs which point at this
               item. If it is any other type then the item itself is the weak reference.

               See also "Perl_sv_add_backref()", "Perl_sv_del_backref()",
               "Perl_sv_kill_backrefs()"

                       SV*     sv_get_backrefs(SV *const sv)

       sv_grow Expands the character buffer in the SV.  If necessary, uses "sv_unref" and
               upgrades the SV to "SVt_PV".  Returns a pointer to the character buffer.  Use the
               "SvGROW" wrapper instead.

                       char*   sv_grow(SV *const sv, STRLEN newlen)

       sv_inc  Auto-increment of the value in the SV, doing string to numeric conversion if
               necessary.  Handles 'get' magic and operator overloading.

                       void    sv_inc(SV *const sv)

       sv_inc_nomg
               Auto-increment of the value in the SV, doing string to numeric conversion if
               necessary.  Handles operator overloading.  Skips handling 'get' magic.

                       void    sv_inc_nomg(SV *const sv)

       sv_insert
               Inserts a string at the specified offset/length within the SV.  Similar to the
               Perl "substr()" function.  Handles get magic.

                       void    sv_insert(SV *const bigstr, const STRLEN offset,
                                         const STRLEN len,
                                         const char *const little,
                                         const STRLEN littlelen)

       sv_insert_flags
               Same as "sv_insert", but the extra "flags" are passed to the "SvPV_force_flags"
               that applies to "bigstr".

                       void    sv_insert_flags(SV *const bigstr,
                                               const STRLEN offset,
                                               const STRLEN len,
                                               const char *little,
                                               const STRLEN littlelen,
                                               const U32 flags)

       sv_isa  Returns a boolean indicating whether the SV is blessed into the specified class.
               This does not check for subtypes; use "sv_derived_from" to verify an inheritance
               relationship.

                       int     sv_isa(SV* sv, const char *const name)

       sv_isobject
               Returns a boolean indicating whether the SV is an RV pointing to a blessed object.
               If the SV is not an RV, or if the object is not blessed, then this will return
               false.

                       int     sv_isobject(SV* sv)

       sv_len  Returns the length of the string in the SV.  Handles magic and type coercion and
               sets the UTF8 flag appropriately.  See also "SvCUR", which gives raw access to the
               "xpv_cur" slot.

                       STRLEN  sv_len(SV *const sv)

       sv_len_utf8
               Returns the number of characters in the string in an SV, counting wide UTF-8 bytes
               as a single character.  Handles magic and type coercion.

                       STRLEN  sv_len_utf8(SV *const sv)

       sv_magic
               Adds magic to an SV.  First upgrades "sv" to type "SVt_PVMG" if necessary, then
               adds a new magic item of type "how" to the head of the magic list.

               See "sv_magicext" (which "sv_magic" now calls) for a description of the handling
               of the "name" and "namlen" arguments.

               You need to use "sv_magicext" to add magic to "SvREADONLY" SVs and also to add
               more than one instance of the same "how".

                       void    sv_magic(SV *const sv, SV *const obj,
                                        const int how, const char *const name,
                                        const I32 namlen)

       sv_magicext
               Adds magic to an SV, upgrading it if necessary.  Applies the supplied "vtable" and
               returns a pointer to the magic added.

               Note that "sv_magicext" will allow things that "sv_magic" will not.  In
               particular, you can add magic to "SvREADONLY" SVs, and add more than one instance
               of the same "how".

               If "namlen" is greater than zero then a "savepvn" copy of "name" is stored, if
               "namlen" is zero then "name" is stored as-is and - as another special case - if
               "(name && namlen == HEf_SVKEY)" then "name" is assumed to contain an SV* and is
               stored as-is with its "REFCNT" incremented.

               (This is now used as a subroutine by "sv_magic".)

                       MAGIC * sv_magicext(SV *const sv, SV *const obj,
                                           const int how,
                                           const MGVTBL *const vtbl,
                                           const char *const name,
                                           const I32 namlen)

       sv_mortalcopy
               Creates a new SV which is a copy of the original SV (using "sv_setsv").  The new
               SV is marked as mortal.  It will be destroyed "soon", either by an explicit call
               to "FREETMPS", or by an implicit call at places such as statement boundaries.  See
               also "sv_newmortal" and "sv_2mortal".

                       SV*     sv_mortalcopy(SV *const oldsv)

       sv_newmortal
               Creates a new null SV which is mortal.  The reference count of the SV is set to 1.
               It will be destroyed "soon", either by an explicit call to "FREETMPS", or by an
               implicit call at places such as statement boundaries.  See also "sv_mortalcopy"
               and "sv_2mortal".

                       SV*     sv_newmortal()

       sv_newref
               Increment an SV's reference count.  Use the "SvREFCNT_inc()" wrapper instead.

                       SV*     sv_newref(SV *const sv)

       sv_pos_b2u
               Converts the value pointed to by "offsetp" from a count of bytes from the start of
               the string, to a count of the equivalent number of UTF-8 chars.  Handles magic and
               type coercion.

               Use "sv_pos_b2u_flags" in preference, which correctly handles strings longer than
               2Gb.

                       void    sv_pos_b2u(SV *const sv, I32 *const offsetp)

       sv_pos_b2u_flags
               Converts "offset" from a count of bytes from the start of the string, to a count
               of the equivalent number of UTF-8 chars.  Handles type coercion.  "flags" is
               passed to "SvPV_flags", and usually should be "SV_GMAGIC|SV_CONST_RETURN" to
               handle magic.

                       STRLEN  sv_pos_b2u_flags(SV *const sv,
                                                STRLEN const offset, U32 flags)

       sv_pos_u2b
               Converts the value pointed to by "offsetp" from a count of UTF-8 chars from the
               start of the string, to a count of the equivalent number of bytes; if "lenp" is
               non-zero, it does the same to "lenp", but this time starting from the offset,
               rather than from the start of the string.  Handles magic and type coercion.

               Use "sv_pos_u2b_flags" in preference, which correctly handles strings longer than
               2Gb.

                       void    sv_pos_u2b(SV *const sv, I32 *const offsetp,
                                          I32 *const lenp)

       sv_pos_u2b_flags
               Converts the offset from a count of UTF-8 chars from the start of the string, to a
               count of the equivalent number of bytes; if "lenp" is non-zero, it does the same
               to "lenp", but this time starting from "offset", rather than from the start of the
               string.  Handles type coercion.  "flags" is passed to "SvPV_flags", and usually
               should be "SV_GMAGIC|SV_CONST_RETURN" to handle magic.

                       STRLEN  sv_pos_u2b_flags(SV *const sv, STRLEN uoffset,
                                                STRLEN *const lenp, U32 flags)

       sv_pvbyten_force
               The backend for the "SvPVbytex_force" macro.  Always use the macro instead.

                       char*   sv_pvbyten_force(SV *const sv, STRLEN *const lp)

       sv_pvn_force
               Get a sensible string out of the SV somehow.  A private implementation of the
               "SvPV_force" macro for compilers which can't cope with complex macro expressions.
               Always use the macro instead.

                       char*   sv_pvn_force(SV* sv, STRLEN* lp)

       sv_pvn_force_flags
               Get a sensible string out of the SV somehow.  If "flags" has the "SV_GMAGIC" bit
               set, will "mg_get" on "sv" if appropriate, else not.  "sv_pvn_force" and
               "sv_pvn_force_nomg" are implemented in terms of this function.  You normally want
               to use the various wrapper macros instead: see "SvPV_force" and "SvPV_force_nomg".

                       char*   sv_pvn_force_flags(SV *const sv,
                                                  STRLEN *const lp,
                                                  const I32 flags)

       sv_pvutf8n_force
               The backend for the "SvPVutf8x_force" macro.  Always use the macro instead.

                       char*   sv_pvutf8n_force(SV *const sv, STRLEN *const lp)

       sv_ref  Returns a SV describing what the SV passed in is a reference to.

               dst can be a SV to be set to the description or NULL, in which case a mortal SV is
               returned.

               If ob is true and the SV is blessed, the description is the class name, otherwise
               it is the type of the SV, "SCALAR", "ARRAY" etc.

                       SV*     sv_ref(SV *dst, const SV *const sv,
                                      const int ob)

       sv_reftype
               Returns a string describing what the SV is a reference to.

               If ob is true and the SV is blessed, the string is the class name, otherwise it is
               the type of the SV, "SCALAR", "ARRAY" etc.

                       const char* sv_reftype(const SV *const sv, const int ob)

       sv_replace
               Make the first argument a copy of the second, then delete the original.  The
               target SV physically takes over ownership of the body of the source SV and
               inherits its flags; however, the target keeps any magic it owns, and any magic in
               the source is discarded.  Note that this is a rather specialist SV copying
               operation; most of the time you'll want to use "sv_setsv" or one of its many macro
               front-ends.

                       void    sv_replace(SV *const sv, SV *const nsv)

       sv_reset
               Underlying implementation for the "reset" Perl function.  Note that the perl-level
               function is vaguely deprecated.

                       void    sv_reset(const char* s, HV *const stash)

       sv_rvweaken
               Weaken a reference: set the "SvWEAKREF" flag on this RV; give the referred-to SV
               "PERL_MAGIC_backref" magic if it hasn't already; and push a back-reference to this
               RV onto the array of backreferences associated with that magic.  If the RV is
               magical, set magic will be called after the RV is cleared.

                       SV*     sv_rvweaken(SV *const sv)

       sv_setiv
               Copies an integer into the given SV, upgrading first if necessary.  Does not
               handle 'set' magic.  See also "sv_setiv_mg".

                       void    sv_setiv(SV *const sv, const IV num)

       sv_setiv_mg
               Like "sv_setiv", but also handles 'set' magic.

                       void    sv_setiv_mg(SV *const sv, const IV i)

       sv_setnv
               Copies a double into the given SV, upgrading first if necessary.  Does not handle
               'set' magic.  See also "sv_setnv_mg".

                       void    sv_setnv(SV *const sv, const NV num)

       sv_setnv_mg
               Like "sv_setnv", but also handles 'set' magic.

                       void    sv_setnv_mg(SV *const sv, const NV num)

       sv_setpv
               Copies a string into an SV.  The string must be terminated with a "NUL" character,
               and not contain embeded "NUL"'s.  Does not handle 'set' magic.  See "sv_setpv_mg".

                       void    sv_setpv(SV *const sv, const char *const ptr)

       sv_setpvf
               Works like "sv_catpvf" but copies the text into the SV instead of appending it.
               Does not handle 'set' magic.  See "sv_setpvf_mg".

                       void    sv_setpvf(SV *const sv, const char *const pat,
                                         ...)

       sv_setpvf_mg
               Like "sv_setpvf", but also handles 'set' magic.

                       void    sv_setpvf_mg(SV *const sv,
                                            const char *const pat, ...)

       sv_setpviv
               Copies an integer into the given SV, also updating its string value.  Does not
               handle 'set' magic.  See "sv_setpviv_mg".

                       void    sv_setpviv(SV *const sv, const IV num)

       sv_setpviv_mg
               Like "sv_setpviv", but also handles 'set' magic.

                       void    sv_setpviv_mg(SV *const sv, const IV iv)

       sv_setpvn
               Copies a string (possibly containing embedded "NUL" characters) into an SV.  The
               "len" parameter indicates the number of bytes to be copied.  If the "ptr" argument
               is NULL the SV will become undefined.  Does not handle 'set' magic.  See
               "sv_setpvn_mg".

                       void    sv_setpvn(SV *const sv, const char *const ptr,
                                         const STRLEN len)

       sv_setpvn_mg
               Like "sv_setpvn", but also handles 'set' magic.

                       void    sv_setpvn_mg(SV *const sv,
                                            const char *const ptr,
                                            const STRLEN len)

       sv_setpvs
               Like "sv_setpvn", but takes a "NUL"-terminated literal string instead of a
               string/length pair.

                       void    sv_setpvs(SV* sv, const char* s)

       sv_setpvs_mg
               Like "sv_setpvn_mg", but takes a "NUL"-terminated literal string instead of a
               string/length pair.

                       void    sv_setpvs_mg(SV* sv, const char* s)

       sv_setpv_bufsize
               Sets the SV to be a string of cur bytes length, with at least len bytes available.
               Ensures that there is a null byte at SvEND.  Returns a char * pointer to the SvPV
               buffer.

                       char  * sv_setpv_bufsize(SV *const sv, const STRLEN cur,
                                                const STRLEN len)

       sv_setpv_mg
               Like "sv_setpv", but also handles 'set' magic.

                       void    sv_setpv_mg(SV *const sv, const char *const ptr)

       sv_setref_iv
               Copies an integer into a new SV, optionally blessing the SV.  The "rv" argument
               will be upgraded to an RV.  That RV will be modified to point to the new SV.  The
               "classname" argument indicates the package for the blessing.  Set "classname" to
               "NULL" to avoid the blessing.  The new SV will have a reference count of 1, and
               the RV will be returned.

                       SV*     sv_setref_iv(SV *const rv,
                                            const char *const classname,
                                            const IV iv)

       sv_setref_nv
               Copies a double into a new SV, optionally blessing the SV.  The "rv" argument will
               be upgraded to an RV.  That RV will be modified to point to the new SV.  The
               "classname" argument indicates the package for the blessing.  Set "classname" to
               "NULL" to avoid the blessing.  The new SV will have a reference count of 1, and
               the RV will be returned.

                       SV*     sv_setref_nv(SV *const rv,
                                            const char *const classname,
                                            const NV nv)

       sv_setref_pv
               Copies a pointer into a new SV, optionally blessing the SV.  The "rv" argument
               will be upgraded to an RV.  That RV will be modified to point to the new SV.  If
               the "pv" argument is "NULL", then "PL_sv_undef" will be placed into the SV.  The
               "classname" argument indicates the package for the blessing.  Set "classname" to
               "NULL" to avoid the blessing.  The new SV will have a reference count of 1, and
               the RV will be returned.

               Do not use with other Perl types such as HV, AV, SV, CV, because those objects
               will become corrupted by the pointer copy process.

               Note that "sv_setref_pvn" copies the string while this copies the pointer.

                       SV*     sv_setref_pv(SV *const rv,
                                            const char *const classname,
                                            void *const pv)

       sv_setref_pvn
               Copies a string into a new SV, optionally blessing the SV.  The length of the
               string must be specified with "n".  The "rv" argument will be upgraded to an RV.
               That RV will be modified to point to the new SV.  The "classname" argument
               indicates the package for the blessing.  Set "classname" to "NULL" to avoid the
               blessing.  The new SV will have a reference count of 1, and the RV will be
               returned.

               Note that "sv_setref_pv" copies the pointer while this copies the string.

                       SV*     sv_setref_pvn(SV *const rv,
                                             const char *const classname,
                                             const char *const pv,
                                             const STRLEN n)

       sv_setref_pvs
               Like "sv_setref_pvn", but takes a "NUL"-terminated literal string instead of a
               string/length pair.

                       SV *    sv_setref_pvs(const char* s)

       sv_setref_uv
               Copies an unsigned integer into a new SV, optionally blessing the SV.  The "rv"
               argument will be upgraded to an RV.  That RV will be modified to point to the new
               SV.  The "classname" argument indicates the package for the blessing.  Set
               "classname" to "NULL" to avoid the blessing.  The new SV will have a reference
               count of 1, and the RV will be returned.

                       SV*     sv_setref_uv(SV *const rv,
                                            const char *const classname,
                                            const UV uv)

       sv_setsv
               Copies the contents of the source SV "ssv" into the destination SV "dsv".  The
               source SV may be destroyed if it is mortal, so don't use this function if the
               source SV needs to be reused.  Does not handle 'set' magic on destination SV.
               Calls 'get' magic on source SV.  Loosely speaking, it performs a copy-by-value,
               obliterating any previous content of the destination.

               You probably want to use one of the assortment of wrappers, such as "SvSetSV",
               "SvSetSV_nosteal", "SvSetMagicSV" and "SvSetMagicSV_nosteal".

                       void    sv_setsv(SV *dstr, SV *sstr)

       sv_setsv_flags
               Copies the contents of the source SV "ssv" into the destination SV "dsv".  The
               source SV may be destroyed if it is mortal, so don't use this function if the
               source SV needs to be reused.  Does not handle 'set' magic.  Loosely speaking, it
               performs a copy-by-value, obliterating any previous content of the destination.
               If the "flags" parameter has the "SV_GMAGIC" bit set, will "mg_get" on "ssv" if
               appropriate, else not.  If the "flags" parameter has the "SV_NOSTEAL" bit set then
               the buffers of temps will not be stolen.  "sv_setsv" and "sv_setsv_nomg" are
               implemented in terms of this function.

               You probably want to use one of the assortment of wrappers, such as "SvSetSV",
               "SvSetSV_nosteal", "SvSetMagicSV" and "SvSetMagicSV_nosteal".

               This is the primary function for copying scalars, and most other copy-ish
               functions and macros use this underneath.

                       void    sv_setsv_flags(SV *dstr, SV *sstr,
                                              const I32 flags)

       sv_setsv_mg
               Like "sv_setsv", but also handles 'set' magic.

                       void    sv_setsv_mg(SV *const dstr, SV *const sstr)

       sv_setuv
               Copies an unsigned integer into the given SV, upgrading first if necessary.  Does
               not handle 'set' magic.  See also "sv_setuv_mg".

                       void    sv_setuv(SV *const sv, const UV num)

       sv_setuv_mg
               Like "sv_setuv", but also handles 'set' magic.

                       void    sv_setuv_mg(SV *const sv, const UV u)

       sv_set_undef
               Equivalent to "sv_setsv(sv, &PL_sv_undef)", but more efficient.  Doesn't handle
               set magic.

               The perl equivalent is "$sv = undef;". Note that it doesn't free any string
               buffer, unlike "undef $sv".

               Introduced in perl 5.26.0.

                       void    sv_set_undef(SV *sv)

       sv_tainted
               Test an SV for taintedness.  Use "SvTAINTED" instead.

                       bool    sv_tainted(SV *const sv)

       sv_true Returns true if the SV has a true value by Perl's rules.  Use the "SvTRUE" macro
               instead, which may call "sv_true()" or may instead use an in-line version.

                       I32     sv_true(SV *const sv)

       sv_unmagic
               Removes all magic of type "type" from an SV.

                       int     sv_unmagic(SV *const sv, const int type)

       sv_unmagicext
               Removes all magic of type "type" with the specified "vtbl" from an SV.

                       int     sv_unmagicext(SV *const sv, const int type,
                                             MGVTBL *vtbl)

       sv_unref_flags
               Unsets the RV status of the SV, and decrements the reference count of whatever was
               being referenced by the RV.  This can almost be thought of as a reversal of
               "newSVrv".  The "cflags" argument can contain "SV_IMMEDIATE_UNREF" to force the
               reference count to be decremented (otherwise the decrementing is conditional on
               the reference count being different from one or the reference being a readonly
               SV).  See "SvROK_off".

                       void    sv_unref_flags(SV *const ref, const U32 flags)

       sv_untaint
               Untaint an SV.  Use "SvTAINTED_off" instead.

                       void    sv_untaint(SV *const sv)

       sv_upgrade
               Upgrade an SV to a more complex form.  Generally adds a new body type to the SV,
               then copies across as much information as possible from the old body.  It croaks
               if the SV is already in a more complex form than requested.  You generally want to
               use the "SvUPGRADE" macro wrapper, which checks the type before calling
               "sv_upgrade", and hence does not croak.  See also "svtype".

                       void    sv_upgrade(SV *const sv, svtype new_type)

       sv_usepvn_flags
               Tells an SV to use "ptr" to find its string value.  Normally the string is stored
               inside the SV, but sv_usepvn allows the SV to use an outside string.  "ptr" should
               point to memory that was allocated by "Newx".  It must be the start of a "Newx"-ed
               block of memory, and not a pointer to the middle of it (beware of "OOK" and copy-
               on-write), and not be from a non-"Newx" memory allocator like "malloc".  The
               string length, "len", must be supplied.  By default this function will "Renew"
               (i.e. realloc, move) the memory pointed to by "ptr", so that pointer should not be
               freed or used by the programmer after giving it to "sv_usepvn", and neither should
               any pointers from "behind" that pointer (e.g. ptr + 1) be used.

               If "flags & SV_SMAGIC" is true, will call "SvSETMAGIC".  If
               "flags" & SV_HAS_TRAILING_NUL> is true, then "ptr[len]" must be "NUL", and the
               realloc will be skipped (i.e. the buffer is actually at least 1 byte longer than
               "len", and already meets the requirements for storing in "SvPVX").

                       void    sv_usepvn_flags(SV *const sv, char* ptr,
                                               const STRLEN len,
                                               const U32 flags)

       sv_utf8_decode
               NOTE: this function is experimental and may change or be removed without notice.

               If the PV of the SV is an octet sequence in Perl's extended UTF-8 and contains a
               multiple-byte character, the "SvUTF8" flag is turned on so that it looks like a
               character.  If the PV contains only single-byte characters, the "SvUTF8" flag
               stays off.  Scans PV for validity and returns FALSE if the PV is invalid UTF-8.

                       bool    sv_utf8_decode(SV *const sv)

       sv_utf8_downgrade
               NOTE: this function is experimental and may change or be removed without notice.

               Attempts to convert the PV of an SV from characters to bytes.  If the PV contains
               a character that cannot fit in a byte, this conversion will fail; in this case,
               either returns false or, if "fail_ok" is not true, croaks.

               This is not a general purpose Unicode to byte encoding interface: use the "Encode"
               extension for that.

                       bool    sv_utf8_downgrade(SV *const sv,
                                                 const bool fail_ok)

       sv_utf8_encode
               Converts the PV of an SV to UTF-8, but then turns the "SvUTF8" flag off so that it
               looks like octets again.

                       void    sv_utf8_encode(SV *const sv)

       sv_utf8_upgrade
               Converts the PV of an SV to its UTF-8-encoded form.  Forces the SV to string form
               if it is not already.  Will "mg_get" on "sv" if appropriate.  Always sets the
               "SvUTF8" flag to avoid future validity checks even if the whole string is the same
               in UTF-8 as not.  Returns the number of bytes in the converted string

               This is not a general purpose byte encoding to Unicode interface: use the Encode
               extension for that.

                       STRLEN  sv_utf8_upgrade(SV *sv)

       sv_utf8_upgrade_flags
               Converts the PV of an SV to its UTF-8-encoded form.  Forces the SV to string form
               if it is not already.  Always sets the SvUTF8 flag to avoid future validity checks
               even if all the bytes are invariant in UTF-8.  If "flags" has "SV_GMAGIC" bit set,
               will "mg_get" on "sv" if appropriate, else not.

               If "flags" has "SV_FORCE_UTF8_UPGRADE" set, this function assumes that the PV will
               expand when converted to UTF-8, and skips the extra work of checking for that.
               Typically this flag is used by a routine that has already parsed the string and
               found such characters, and passes this information on so that the work doesn't
               have to be repeated.

               Returns the number of bytes in the converted string.

               This is not a general purpose byte encoding to Unicode interface: use the Encode
               extension for that.

                       STRLEN  sv_utf8_upgrade_flags(SV *const sv,
                                                     const I32 flags)

       sv_utf8_upgrade_flags_grow
               Like "sv_utf8_upgrade_flags", but has an additional parameter "extra", which is
               the number of unused bytes the string of "sv" is guaranteed to have free after it
               upon return.  This allows the caller to reserve extra space that it intends to
               fill, to avoid extra grows.

               "sv_utf8_upgrade", "sv_utf8_upgrade_nomg", and "sv_utf8_upgrade_flags" are
               implemented in terms of this function.

               Returns the number of bytes in the converted string (not including the spares).

                       STRLEN  sv_utf8_upgrade_flags_grow(SV *const sv,
                                                          const I32 flags,
                                                          STRLEN extra)

       sv_utf8_upgrade_nomg
               Like "sv_utf8_upgrade", but doesn't do magic on "sv".

                       STRLEN  sv_utf8_upgrade_nomg(SV *sv)

       sv_vcatpvf
               Processes its arguments like "sv_catpvfn" called with a non-null C-style variable
               argument list, and appends the formatted output to an SV.  Does not handle 'set'
               magic.  See "sv_vcatpvf_mg".

               Usually used via its frontend "sv_catpvf".

                       void    sv_vcatpvf(SV *const sv, const char *const pat,
                                          va_list *const args)

       sv_vcatpvfn
                       void    sv_vcatpvfn(SV *const sv, const char *const pat,
                                           const STRLEN patlen,
                                           va_list *const args,
                                           SV **const svargs, const I32 svmax,
                                           bool *const maybe_tainted)

       sv_vcatpvfn_flags
               Processes its arguments like "vsprintf" and appends the formatted output to an SV.
               Uses an array of SVs if the C-style variable argument list is missing ("NULL").
               Argument reordering (using format specifiers like "%2$d" or "%*2$d") is supported
               only when using an array of SVs; using a C-style "va_list" argument list with a
               format string that uses argument reordering will yield an exception.

               When running with taint checks enabled, indicates via "maybe_tainted" if results
               are untrustworthy (often due to the use of locales).

               If called as "sv_vcatpvfn" or flags has the "SV_GMAGIC" bit set, calls get magic.

               Usually used via one of its frontends "sv_vcatpvf" and "sv_vcatpvf_mg".

                       void    sv_vcatpvfn_flags(SV *const sv,
                                                 const char *const pat,
                                                 const STRLEN patlen,
                                                 va_list *const args,
                                                 SV **const svargs,
                                                 const I32 svmax,
                                                 bool *const maybe_tainted,
                                                 const U32 flags)

       sv_vcatpvf_mg
               Like "sv_vcatpvf", but also handles 'set' magic.

               Usually used via its frontend "sv_catpvf_mg".

                       void    sv_vcatpvf_mg(SV *const sv,
                                             const char *const pat,
                                             va_list *const args)

       sv_vsetpvf
               Works like "sv_vcatpvf" but copies the text into the SV instead of appending it.
               Does not handle 'set' magic.  See "sv_vsetpvf_mg".

               Usually used via its frontend "sv_setpvf".

                       void    sv_vsetpvf(SV *const sv, const char *const pat,
                                          va_list *const args)

       sv_vsetpvfn
               Works like "sv_vcatpvfn" but copies the text into the SV instead of appending it.

               Usually used via one of its frontends "sv_vsetpvf" and "sv_vsetpvf_mg".

                       void    sv_vsetpvfn(SV *const sv, const char *const pat,
                                           const STRLEN patlen,
                                           va_list *const args,
                                           SV **const svargs, const I32 svmax,
                                           bool *const maybe_tainted)

       sv_vsetpvf_mg
               Like "sv_vsetpvf", but also handles 'set' magic.

               Usually used via its frontend "sv_setpvf_mg".

                       void    sv_vsetpvf_mg(SV *const sv,
                                             const char *const pat,
                                             va_list *const args)

SV Flags

       SVt_INVLIST
               Type flag for scalars.  See "svtype".

       SVt_IV  Type flag for scalars.  See "svtype".

       SVt_NULL
               Type flag for scalars.  See "svtype".

       SVt_NV  Type flag for scalars.  See "svtype".

       SVt_PV  Type flag for scalars.  See "svtype".

       SVt_PVAV
               Type flag for arrays.  See "svtype".

       SVt_PVCV
               Type flag for subroutines.  See "svtype".

       SVt_PVFM
               Type flag for formats.  See "svtype".

       SVt_PVGV
               Type flag for typeglobs.  See "svtype".

       SVt_PVHV
               Type flag for hashes.  See "svtype".

       SVt_PVIO
               Type flag for I/O objects.  See "svtype".

       SVt_PVIV
               Type flag for scalars.  See "svtype".

       SVt_PVLV
               Type flag for scalars.  See "svtype".

       SVt_PVMG
               Type flag for scalars.  See "svtype".

       SVt_PVNV
               Type flag for scalars.  See "svtype".

       SVt_REGEXP
               Type flag for regular expressions.  See "svtype".

       svtype  An enum of flags for Perl types.  These are found in the file sv.h in the "svtype"
               enum.  Test these flags with the "SvTYPE" macro.

               The types are:

                   SVt_NULL
                   SVt_IV
                   SVt_NV
                   SVt_RV
                   SVt_PV
                   SVt_PVIV
                   SVt_PVNV
                   SVt_PVMG
                   SVt_INVLIST
                   SVt_REGEXP
                   SVt_PVGV
                   SVt_PVLV
                   SVt_PVAV
                   SVt_PVHV
                   SVt_PVCV
                   SVt_PVFM
                   SVt_PVIO

               These are most easily explained from the bottom up.

               "SVt_PVIO" is for I/O objects, "SVt_PVFM" for formats, "SVt_PVCV" for subroutines,
               "SVt_PVHV" for hashes and "SVt_PVAV" for arrays.

               All the others are scalar types, that is, things that can be bound to a "$"
               variable.  For these, the internal types are mostly orthogonal to types in the
               Perl language.

               Hence, checking "SvTYPE(sv) < SVt_PVAV" is the best way to see whether something
               is a scalar.

               "SVt_PVGV" represents a typeglob.  If "!SvFAKE(sv)", then it is a real,
               incoercible typeglob.  If "SvFAKE(sv)", then it is a scalar to which a typeglob
               has been assigned.  Assigning to it again will stop it from being a typeglob.
               "SVt_PVLV" represents a scalar that delegates to another scalar behind the scenes.
               It is used, e.g., for the return value of "substr" and for tied hash and array
               elements.  It can hold any scalar value, including a typeglob.  "SVt_REGEXP" is
               for regular expressions.  "SVt_INVLIST" is for Perl core internal use only.

               "SVt_PVMG" represents a "normal" scalar (not a typeglob, regular expression, or
               delegate).  Since most scalars do not need all the internal fields of a PVMG, we
               save memory by allocating smaller structs when possible.  All the other types are
               just simpler forms of "SVt_PVMG", with fewer internal fields.  "SVt_NULL" can only
               hold undef.  "SVt_IV" can hold undef, an integer, or a reference.  ("SVt_RV" is an
               alias for "SVt_IV", which exists for backward compatibility.)  "SVt_NV" can hold
               any of those or a double.  "SVt_PV" can only hold "undef" or a string.  "SVt_PVIV"
               is a superset of "SVt_PV" and "SVt_IV".  "SVt_PVNV" is similar.  "SVt_PVMG" can
               hold anything "SVt_PVNV" can hold, but it can, but does not have to, be blessed or
               magical.

SV Manipulation Functions

       boolSV  Returns a true SV if "b" is a true value, or a false SV if "b" is 0.

               See also "PL_sv_yes" and "PL_sv_no".

                       SV *    boolSV(bool b)

       croak_xs_usage
               A specialised variant of "croak()" for emitting the usage message for xsubs

                   croak_xs_usage(cv, "eee_yow");

               works out the package name and subroutine name from "cv", and then calls
               "croak()".  Hence if "cv" is &ouch::awk, it would call "croak" as:

                Perl_croak(aTHX_ "Usage: %" SVf "::%" SVf "(%s)", "ouch" "awk",
                                                                    "eee_yow");

                       void    croak_xs_usage(const CV *const cv,
                                              const char *const params)

       get_sv  Returns the SV of the specified Perl scalar.  "flags" are passed to "gv_fetchpv".
               If "GV_ADD" is set and the Perl variable does not exist then it will be created.
               If "flags" is zero and the variable does not exist then NULL is returned.

               NOTE: the perl_ form of this function is deprecated.

                       SV*     get_sv(const char *name, I32 flags)

       newRV_inc
               Creates an RV wrapper for an SV.  The reference count for the original SV is
               incremented.

                       SV*     newRV_inc(SV* sv)

       newSVpadname
               NOTE: this function is experimental and may change or be removed without notice.

               Creates a new SV containing the pad name.

                       SV*     newSVpadname(PADNAME *pn)

       newSVpvn_utf8
               Creates a new SV and copies a string (which may contain "NUL" ("\0") characters)
               into it.  If "utf8" is true, calls "SvUTF8_on" on the new SV.  Implemented as a
               wrapper around "newSVpvn_flags".

                       SV*     newSVpvn_utf8(NULLOK const char* s, STRLEN len,
                                             U32 utf8)

       sv_catpvn_nomg
               Like "sv_catpvn" but doesn't process magic.

                       void    sv_catpvn_nomg(SV* sv, const char* ptr,
                                              STRLEN len)

       sv_catpv_nomg
               Like "sv_catpv" but doesn't process magic.

                       void    sv_catpv_nomg(SV* sv, const char* ptr)

       sv_catsv_nomg
               Like "sv_catsv" but doesn't process magic.

                       void    sv_catsv_nomg(SV* dsv, SV* ssv)

       SvCUR   Returns the length of the string which is in the SV.  See "SvLEN".

                       STRLEN  SvCUR(SV* sv)

       SvCUR_set
               Set the current length of the string which is in the SV.  See "SvCUR" and
               "SvIV_set">.

                       void    SvCUR_set(SV* sv, STRLEN len)

       sv_derived_from
               Exactly like "sv_derived_from_pv", but doesn't take a "flags" parameter.

                       bool    sv_derived_from(SV* sv, const char *const name)

       sv_derived_from_pv
               Exactly like "sv_derived_from_pvn", but takes a nul-terminated string instead of a
               string/length pair.

                       bool    sv_derived_from_pv(SV* sv,
                                                  const char *const name,
                                                  U32 flags)

       sv_derived_from_pvn
               Returns a boolean indicating whether the SV is derived from the specified class at
               the C level.  To check derivation at the Perl level, call "isa()" as a normal Perl
               method.

               Currently, the only significant value for "flags" is SVf_UTF8.

                       bool    sv_derived_from_pvn(SV* sv,
                                                   const char *const name,
                                                   const STRLEN len, U32 flags)

       sv_derived_from_sv
               Exactly like "sv_derived_from_pvn", but takes the name string in the form of an SV
               instead of a string/length pair.

                       bool    sv_derived_from_sv(SV* sv, SV *namesv,
                                                  U32 flags)

       sv_does Like "sv_does_pv", but doesn't take a "flags" parameter.

                       bool    sv_does(SV* sv, const char *const name)

       sv_does_pv
               Like "sv_does_sv", but takes a nul-terminated string instead of an SV.

                       bool    sv_does_pv(SV* sv, const char *const name,
                                          U32 flags)

       sv_does_pvn
               Like "sv_does_sv", but takes a string/length pair instead of an SV.

                       bool    sv_does_pvn(SV* sv, const char *const name,
                                           const STRLEN len, U32 flags)

       sv_does_sv
               Returns a boolean indicating whether the SV performs a specific, named role.  The
               SV can be a Perl object or the name of a Perl class.

                       bool    sv_does_sv(SV* sv, SV* namesv, U32 flags)

       SvEND   Returns a pointer to the spot just after the last character in the string which is
               in the SV, where there is usually a trailing "NUL" character (even though Perl
               scalars do not strictly require it).  See "SvCUR".  Access the character as
               "*(SvEND(sv))".

               Warning: If "SvCUR" is equal to "SvLEN", then "SvEND" points to unallocated
               memory.

                       char*   SvEND(SV* sv)

       SvGAMAGIC
               Returns true if the SV has get magic or overloading.  If either is true then the
               scalar is active data, and has the potential to return a new value every time it
               is accessed.  Hence you must be careful to only read it once per user logical
               operation and work with that returned value.  If neither is true then the scalar's
               value cannot change unless written to.

                       U32     SvGAMAGIC(SV* sv)

       SvGROW  Expands the character buffer in the SV so that it has room for the indicated
               number of bytes (remember to reserve space for an extra trailing "NUL" character).
               Calls "sv_grow" to perform the expansion if necessary.  Returns a pointer to the
               character buffer.  SV must be of type >= "SVt_PV".  One alternative is to call
               "sv_grow" if you are not sure of the type of SV.

               You might mistakenly think that "len" is the number of bytes to add to the
               existing size, but instead it is the total size "sv" should be.

                       char *  SvGROW(SV* sv, STRLEN len)

       SvIOK   Returns a U32 value indicating whether the SV contains an integer.

                       U32     SvIOK(SV* sv)

       SvIOK_notUV
               Returns a boolean indicating whether the SV contains a signed integer.

                       bool    SvIOK_notUV(SV* sv)

       SvIOK_off
               Unsets the IV status of an SV.

                       void    SvIOK_off(SV* sv)

       SvIOK_on
               Tells an SV that it is an integer.

                       void    SvIOK_on(SV* sv)

       SvIOK_only
               Tells an SV that it is an integer and disables all other "OK" bits.

                       void    SvIOK_only(SV* sv)

       SvIOK_only_UV
               Tells an SV that it is an unsigned integer and disables all other "OK" bits.

                       void    SvIOK_only_UV(SV* sv)

       SvIOKp  Returns a U32 value indicating whether the SV contains an integer.  Checks the
               private setting.  Use "SvIOK" instead.

                       U32     SvIOKp(SV* sv)

       SvIOK_UV
               Returns a boolean indicating whether the SV contains an integer that must be
               interpreted as unsigned.  A non-negative integer whose value is within the range
               of both an IV and a UV may be be flagged as either "SvUOK" or "SVIOK".

                       bool    SvIOK_UV(SV* sv)

       SvIsCOW Returns a U32 value indicating whether the SV is Copy-On-Write (either shared hash
               key scalars, or full Copy On Write scalars if 5.9.0 is configured for COW).

                       U32     SvIsCOW(SV* sv)

       SvIsCOW_shared_hash
               Returns a boolean indicating whether the SV is Copy-On-Write shared hash key
               scalar.

                       bool    SvIsCOW_shared_hash(SV* sv)

       SvIV    Coerces the given SV to IV and returns it.  The returned value in many
               circumstances will get stored in "sv"'s IV slot, but not in all cases.  (Use
               "sv_setiv" to make sure it does).

               See "SvIVx" for a version which guarantees to evaluate "sv" only once.

                       IV      SvIV(SV* sv)

       SvIV_nomg
               Like "SvIV" but doesn't process magic.

                       IV      SvIV_nomg(SV* sv)

       SvIV_set
               Set the value of the IV pointer in sv to val.  It is possible to perform the same
               function of this macro with an lvalue assignment to "SvIVX".  With future Perls,
               however, it will be more efficient to use "SvIV_set" instead of the lvalue
               assignment to "SvIVX".

                       void    SvIV_set(SV* sv, IV val)

       SvIVX   Returns the raw value in the SV's IV slot, without checks or conversions.  Only
               use when you are sure "SvIOK" is true.  See also "SvIV".

                       IV      SvIVX(SV* sv)

       SvIVx   Coerces the given SV to IV and returns it.  The returned value in many
               circumstances will get stored in "sv"'s IV slot, but not in all cases.  (Use
               "sv_setiv" to make sure it does).

               This form guarantees to evaluate "sv" only once.  Only use this if "sv" is an
               expression with side effects, otherwise use the more efficient "SvIV".

                       IV      SvIVx(SV* sv)

       SvLEN   Returns the size of the string buffer in the SV, not including any part
               attributable to "SvOOK".  See "SvCUR".

                       STRLEN  SvLEN(SV* sv)

       SvLEN_set
               Set the size of the string buffer for the SV. See "SvLEN".

                       void    SvLEN_set(SV* sv, STRLEN len)

       SvMAGIC_set
               Set the value of the MAGIC pointer in "sv" to val.  See "SvIV_set".

                       void    SvMAGIC_set(SV* sv, MAGIC* val)

       SvNIOK  Returns a U32 value indicating whether the SV contains a number, integer or
               double.

                       U32     SvNIOK(SV* sv)

       SvNIOK_off
               Unsets the NV/IV status of an SV.

                       void    SvNIOK_off(SV* sv)

       SvNIOKp Returns a U32 value indicating whether the SV contains a number, integer or
               double.  Checks the private setting.  Use "SvNIOK" instead.

                       U32     SvNIOKp(SV* sv)

       SvNOK   Returns a U32 value indicating whether the SV contains a double.

                       U32     SvNOK(SV* sv)

       SvNOK_off
               Unsets the NV status of an SV.

                       void    SvNOK_off(SV* sv)

       SvNOK_on
               Tells an SV that it is a double.

                       void    SvNOK_on(SV* sv)

       SvNOK_only
               Tells an SV that it is a double and disables all other OK bits.

                       void    SvNOK_only(SV* sv)

       SvNOKp  Returns a U32 value indicating whether the SV contains a double.  Checks the
               private setting.  Use "SvNOK" instead.

                       U32     SvNOKp(SV* sv)

       SvNV    Coerces the given SV to NV and returns it.  The returned value in many
               circumstances will get stored in "sv"'s NV slot, but not in all cases.  (Use
               "sv_setnv" to make sure it does).

               See "SvNVx" for a version which guarantees to evaluate "sv" only once.

                       NV      SvNV(SV* sv)

       SvNV_nomg
               Like "SvNV" but doesn't process magic.

                       NV      SvNV_nomg(SV* sv)

       SvNV_set
               Set the value of the NV pointer in "sv" to val.  See "SvIV_set".

                       void    SvNV_set(SV* sv, NV val)

       SvNVX   Returns the raw value in the SV's NV slot, without checks or conversions.  Only
               use when you are sure "SvNOK" is true.  See also "SvNV".

                       NV      SvNVX(SV* sv)

       SvNVx   Coerces the given SV to NV and returns it.  The returned value in many
               circumstances will get stored in "sv"'s NV slot, but not in all cases.  (Use
               "sv_setnv" to make sure it does).

               This form guarantees to evaluate "sv" only once.  Only use this if "sv" is an
               expression with side effects, otherwise use the more efficient "SvNV".

                       NV      SvNVx(SV* sv)

       SvOK    Returns a U32 value indicating whether the value is defined.  This is only
               meaningful for scalars.

                       U32     SvOK(SV* sv)

       SvOOK   Returns a U32 indicating whether the pointer to the string buffer is offset.  This
               hack is used internally to speed up removal of characters from the beginning of a
               "SvPV".  When "SvOOK" is true, then the start of the allocated string buffer is
               actually "SvOOK_offset()" bytes before "SvPVX".  This offset used to be stored in
               "SvIVX", but is now stored within the spare part of the buffer.

                       U32     SvOOK(SV* sv)

       SvOOK_offset
               Reads into "len" the offset from "SvPVX" back to the true start of the allocated
               buffer, which will be non-zero if "sv_chop" has been used to efficiently remove
               characters from start of the buffer.  Implemented as a macro, which takes the
               address of "len", which must be of type "STRLEN".  Evaluates "sv" more than once.
               Sets "len" to 0 if "SvOOK(sv)" is false.

                       void    SvOOK_offset(NN SV*sv, STRLEN len)

       SvPOK   Returns a U32 value indicating whether the SV contains a character string.

                       U32     SvPOK(SV* sv)

       SvPOK_off
               Unsets the PV status of an SV.

                       void    SvPOK_off(SV* sv)

       SvPOK_on
               Tells an SV that it is a string.

                       void    SvPOK_on(SV* sv)

       SvPOK_only
               Tells an SV that it is a string and disables all other "OK" bits.  Will also turn
               off the UTF-8 status.

                       void    SvPOK_only(SV* sv)

       SvPOK_only_UTF8
               Tells an SV that it is a string and disables all other "OK" bits, and leaves the
               UTF-8 status as it was.

                       void    SvPOK_only_UTF8(SV* sv)

       SvPOKp  Returns a U32 value indicating whether the SV contains a character string.  Checks
               the private setting.  Use "SvPOK" instead.

                       U32     SvPOKp(SV* sv)

       SvPV    Returns a pointer to the string in the SV, or a stringified form of the SV if the
               SV does not contain a string.  The SV may cache the stringified version becoming
               "SvPOK".  Handles 'get' magic.  The "len" variable will be set to the length of
               the string (this is a macro, so don't use &len).  See also "SvPVx" for a version
               which guarantees to evaluate "sv" only once.

               Note that there is no guarantee that the return value of "SvPV()" is equal to
               "SvPVX(sv)", or that "SvPVX(sv)" contains valid data, or that successive calls to
               "SvPV(sv)" will return the same pointer value each time.  This is due to the way
               that things like overloading and Copy-On-Write are handled.  In these cases, the
               return value may point to a temporary buffer or similar.  If you absolutely need
               the "SvPVX" field to be valid (for example, if you intend to write to it), then
               see "SvPV_force".

                       char*   SvPV(SV* sv, STRLEN len)

       SvPVbyte
               Like "SvPV", but converts "sv" to byte representation first if necessary.

                       char*   SvPVbyte(SV* sv, STRLEN len)

       SvPVbyte_force
               Like "SvPV_force", but converts "sv" to byte representation first if necessary.

                       char*   SvPVbyte_force(SV* sv, STRLEN len)

       SvPVbyte_nolen
               Like "SvPV_nolen", but converts "sv" to byte representation first if necessary.

                       char*   SvPVbyte_nolen(SV* sv)

       SvPVbytex
               Like "SvPV", but converts "sv" to byte representation first if necessary.
               Guarantees to evaluate "sv" only once; use the more efficient "SvPVbyte"
               otherwise.

                       char*   SvPVbytex(SV* sv, STRLEN len)

       SvPVbytex_force
               Like "SvPV_force", but converts "sv" to byte representation first if necessary.
               Guarantees to evaluate "sv" only once; use the more efficient "SvPVbyte_force"
               otherwise.

                       char*   SvPVbytex_force(SV* sv, STRLEN len)

       SvPVCLEAR
               Ensures that sv is a SVt_PV and that its SvCUR is 0, and that it is properly null
               terminated. Equivalent to sv_setpvs(""), but more efficient.

                       char *  SvPVCLEAR(SV* sv)

       SvPV_force
               Like "SvPV" but will force the SV into containing a string ("SvPOK"), and only a
               string ("SvPOK_only"), by hook or by crook.  You need force if you are going to
               update the "SvPVX" directly.  Processes get magic.

               Note that coercing an arbitrary scalar into a plain PV will potentially strip
               useful data from it.  For example if the SV was "SvROK", then the referent will
               have its reference count decremented, and the SV itself may be converted to an
               "SvPOK" scalar with a string buffer containing a value such as "ARRAY(0x1234)".

                       char*   SvPV_force(SV* sv, STRLEN len)

       SvPV_force_nomg
               Like "SvPV_force", but doesn't process get magic.

                       char*   SvPV_force_nomg(SV* sv, STRLEN len)

       SvPV_nolen
               Like "SvPV" but doesn't set a length variable.

                       char*   SvPV_nolen(SV* sv)

       SvPV_nomg
               Like "SvPV" but doesn't process magic.

                       char*   SvPV_nomg(SV* sv, STRLEN len)

       SvPV_nomg_nolen
               Like "SvPV_nolen" but doesn't process magic.

                       char*   SvPV_nomg_nolen(SV* sv)

       SvPV_set
               This is probably not what you want to use, you probably wanted "sv_usepvn_flags"
               or "sv_setpvn" or "sv_setpvs".

               Set the value of the PV pointer in "sv" to the Perl allocated "NUL"-terminated
               string "val".  See also "SvIV_set".

               Remember to free the previous PV buffer. There are many things to check.  Beware
               that the existing pointer may be involved in copy-on-write or other mischief, so
               do "SvOOK_off(sv)" and use "sv_force_normal" or "SvPV_force" (or check the
               "SvIsCOW" flag) first to make sure this modification is safe. Then finally, if it
               is not a COW, call "SvPV_free" to free the previous PV buffer.

                       void    SvPV_set(SV* sv, char* val)

       SvPVutf8
               Like "SvPV", but converts "sv" to UTF-8 first if necessary.

                       char*   SvPVutf8(SV* sv, STRLEN len)

       SvPVutf8x
               Like "SvPV", but converts "sv" to UTF-8 first if necessary.  Guarantees to
               evaluate "sv" only once; use the more efficient "SvPVutf8" otherwise.

                       char*   SvPVutf8x(SV* sv, STRLEN len)

       SvPVutf8x_force
               Like "SvPV_force", but converts "sv" to UTF-8 first if necessary.  Guarantees to
               evaluate "sv" only once; use the more efficient "SvPVutf8_force" otherwise.

                       char*   SvPVutf8x_force(SV* sv, STRLEN len)

       SvPVutf8_force
               Like "SvPV_force", but converts "sv" to UTF-8 first if necessary.

                       char*   SvPVutf8_force(SV* sv, STRLEN len)

       SvPVutf8_nolen
               Like "SvPV_nolen", but converts "sv" to UTF-8 first if necessary.

                       char*   SvPVutf8_nolen(SV* sv)

       SvPVX   Returns a pointer to the physical string in the SV.  The SV must contain a string.
               Prior to 5.9.3 it is not safe to execute this macro unless the SV's type >=
               "SVt_PV".

               This is also used to store the name of an autoloaded subroutine in an XS AUTOLOAD
               routine.  See "Autoloading with XSUBs" in perlguts.

                       char*   SvPVX(SV* sv)

       SvPVx   A version of "SvPV" which guarantees to evaluate "sv" only once.  Only use this if
               "sv" is an expression with side effects, otherwise use the more efficient "SvPV".

                       char*   SvPVx(SV* sv, STRLEN len)

       SvREADONLY
               Returns true if the argument is readonly, otherwise returns false.  Exposed to to
               perl code via Internals::SvREADONLY().

                       U32     SvREADONLY(SV* sv)

       SvREADONLY_off
               Mark an object as not-readonly. Exactly what this mean depends on the object type.
               Exposed to perl code via Internals::SvREADONLY().

                       U32     SvREADONLY_off(SV* sv)

       SvREADONLY_on
               Mark an object as readonly. Exactly what this means depends on the object type.
               Exposed to perl code via Internals::SvREADONLY().

                       U32     SvREADONLY_on(SV* sv)

       SvREFCNT
               Returns the value of the object's reference count. Exposed to perl code via
               Internals::SvREFCNT().

                       U32     SvREFCNT(SV* sv)

       SvREFCNT_dec
               Decrements the reference count of the given SV.  "sv" may be "NULL".

                       void    SvREFCNT_dec(SV* sv)

       SvREFCNT_dec_NN
               Same as "SvREFCNT_dec", but can only be used if you know "sv" is not "NULL".
               Since we don't have to check the NULLness, it's faster and smaller.

                       void    SvREFCNT_dec_NN(SV* sv)

       SvREFCNT_inc
               Increments the reference count of the given SV, returning the SV.

               All of the following "SvREFCNT_inc"* macros are optimized versions of
               "SvREFCNT_inc", and can be replaced with "SvREFCNT_inc".

                       SV*     SvREFCNT_inc(SV* sv)

       SvREFCNT_inc_NN
               Same as "SvREFCNT_inc", but can only be used if you know "sv" is not "NULL".
               Since we don't have to check the NULLness, it's faster and smaller.

                       SV*     SvREFCNT_inc_NN(SV* sv)

       SvREFCNT_inc_simple
               Same as "SvREFCNT_inc", but can only be used with expressions without side
               effects.  Since we don't have to store a temporary value, it's faster.

                       SV*     SvREFCNT_inc_simple(SV* sv)

       SvREFCNT_inc_simple_NN
               Same as "SvREFCNT_inc_simple", but can only be used if you know "sv" is not
               "NULL".  Since we don't have to check the NULLness, it's faster and smaller.

                       SV*     SvREFCNT_inc_simple_NN(SV* sv)

       SvREFCNT_inc_simple_void
               Same as "SvREFCNT_inc_simple", but can only be used if you don't need the return
               value.  The macro doesn't need to return a meaningful value.

                       void    SvREFCNT_inc_simple_void(SV* sv)

       SvREFCNT_inc_simple_void_NN
               Same as "SvREFCNT_inc", but can only be used if you don't need the return value,
               and you know that "sv" is not "NULL".  The macro doesn't need to return a
               meaningful value, or check for NULLness, so it's smaller and faster.

                       void    SvREFCNT_inc_simple_void_NN(SV* sv)

       SvREFCNT_inc_void
               Same as "SvREFCNT_inc", but can only be used if you don't need the return value.
               The macro doesn't need to return a meaningful value.

                       void    SvREFCNT_inc_void(SV* sv)

       SvREFCNT_inc_void_NN
               Same as "SvREFCNT_inc", but can only be used if you don't need the return value,
               and you know that "sv" is not "NULL".  The macro doesn't need to return a
               meaningful value, or check for NULLness, so it's smaller and faster.

                       void    SvREFCNT_inc_void_NN(SV* sv)

       sv_report_used
               Dump the contents of all SVs not yet freed (debugging aid).

                       void    sv_report_used()

       SvROK   Tests if the SV is an RV.

                       U32     SvROK(SV* sv)

       SvROK_off
               Unsets the RV status of an SV.

                       void    SvROK_off(SV* sv)

       SvROK_on
               Tells an SV that it is an RV.

                       void    SvROK_on(SV* sv)

       SvRV    Dereferences an RV to return the SV.

                       SV*     SvRV(SV* sv)

       SvRV_set
               Set the value of the RV pointer in "sv" to val.  See "SvIV_set".

                       void    SvRV_set(SV* sv, SV* val)

       sv_setsv_nomg
               Like "sv_setsv" but doesn't process magic.

                       void    sv_setsv_nomg(SV* dsv, SV* ssv)

       SvSTASH Returns the stash of the SV.

                       HV*     SvSTASH(SV* sv)

       SvSTASH_set
               Set the value of the STASH pointer in "sv" to val.  See "SvIV_set".

                       void    SvSTASH_set(SV* sv, HV* val)

       SvTAINT Taints an SV if tainting is enabled, and if some input to the current expression
               is tainted--usually a variable, but possibly also implicit inputs such as locale
               settings.  "SvTAINT" propagates that taintedness to the outputs of an expression
               in a pessimistic fashion; i.e., without paying attention to precisely which
               outputs are influenced by which inputs.

                       void    SvTAINT(SV* sv)

       SvTAINTED
               Checks to see if an SV is tainted.  Returns TRUE if it is, FALSE if not.

                       bool    SvTAINTED(SV* sv)

       SvTAINTED_off
               Untaints an SV.  Be very careful with this routine, as it short-circuits some of
               Perl's fundamental security features.  XS module authors should not use this
               function unless they fully understand all the implications of unconditionally
               untainting the value.  Untainting should be done in the standard perl fashion, via
               a carefully crafted regexp, rather than directly untainting variables.

                       void    SvTAINTED_off(SV* sv)

       SvTAINTED_on
               Marks an SV as tainted if tainting is enabled.

                       void    SvTAINTED_on(SV* sv)

       SvTRUE  Returns a boolean indicating whether Perl would evaluate the SV as true or false.
               See "SvOK" for a defined/undefined test.  Handles 'get' magic unless the scalar is
               already "SvPOK", "SvIOK" or "SvNOK" (the public, not the private flags).

                       bool    SvTRUE(SV* sv)

       SvTRUE_nomg
               Returns a boolean indicating whether Perl would evaluate the SV as true or false.
               See "SvOK" for a defined/undefined test.  Does not handle 'get' magic.

                       bool    SvTRUE_nomg(SV* sv)

       SvTYPE  Returns the type of the SV.  See "svtype".

                       svtype  SvTYPE(SV* sv)

       SvUOK   Returns a boolean indicating whether the SV contains an integer that must be
               interpreted as unsigned.  A non-negative integer whose value is within the range
               of both an IV and a UV may be be flagged as either "SvUOK" or "SVIOK".

                       bool    SvUOK(SV* sv)

       SvUPGRADE
               Used to upgrade an SV to a more complex form.  Uses "sv_upgrade" to perform the
               upgrade if necessary.  See "svtype".

                       void    SvUPGRADE(SV* sv, svtype type)

       SvUTF8  Returns a U32 value indicating the UTF-8 status of an SV.  If things are set-up
               properly, this indicates whether or not the SV contains UTF-8 encoded data.  You
               should use this after a call to "SvPV()" or one of its variants, in case any call
               to string overloading updates the internal flag.

               If you want to take into account the bytes pragma, use "DO_UTF8" instead.

                       U32     SvUTF8(SV* sv)

       sv_utf8_upgrade_nomg
               Like "sv_utf8_upgrade", but doesn't do magic on "sv".

                       STRLEN  sv_utf8_upgrade_nomg(NN SV *sv)

       SvUTF8_off
               Unsets the UTF-8 status of an SV (the data is not changed, just the flag).  Do not
               use frivolously.

                       void    SvUTF8_off(SV *sv)

       SvUTF8_on
               Turn on the UTF-8 status of an SV (the data is not changed, just the flag).  Do
               not use frivolously.

                       void    SvUTF8_on(SV *sv)

       SvUV    Coerces the given SV to UV and returns it.  The returned value in many
               circumstances will get stored in "sv"'s UV slot, but not in all cases.  (Use
               "sv_setuv" to make sure it does).

               See "SvUVx" for a version which guarantees to evaluate "sv" only once.

                       UV      SvUV(SV* sv)

       SvUV_nomg
               Like "SvUV" but doesn't process magic.

                       UV      SvUV_nomg(SV* sv)

       SvUV_set
               Set the value of the UV pointer in "sv" to val.  See "SvIV_set".

                       void    SvUV_set(SV* sv, UV val)

       SvUVX   Returns the raw value in the SV's UV slot, without checks or conversions.  Only
               use when you are sure "SvIOK" is true.  See also "SvUV".

                       UV      SvUVX(SV* sv)

       SvUVx   Coerces the given SV to UV and returns it.  The returned value in many
               circumstances will get stored in "sv"'s UV slot, but not in all cases.  (Use
               "sv_setuv" to make sure it does).

               This form guarantees to evaluate "sv" only once.  Only use this if "sv" is an
               expression with side effects, otherwise use the more efficient "SvUV".

                       UV      SvUVx(SV* sv)

       SvVOK   Returns a boolean indicating whether the SV contains a v-string.

                       bool    SvVOK(SV* sv)

Unicode Support

       "Unicode Support" in perlguts has an introduction to this API.

       See also "Character classification", and "Character case changing".  Various functions
       outside this section also work specially with Unicode.  Search for the string "utf8" in
       this document.

       BOM_UTF8
               This is a macro that evaluates to a string constant of the  UTF-8 bytes that
               define the Unicode BYTE ORDER MARK (U+FEFF) for the platform that perl is compiled
               on.  This allows code to use a mnemonic for this character that works on both
               ASCII and EBCDIC platforms.  "sizeof(BOM_UTF8) - 1" can be used to get its length
               in bytes.

       bytes_cmp_utf8
               Compares the sequence of characters (stored as octets) in "b", "blen" with the
               sequence of characters (stored as UTF-8) in "u", "ulen".  Returns 0 if they are
               equal, -1 or -2 if the first string is less than the second string, +1 or +2 if
               the first string is greater than the second string.

               -1 or +1 is returned if the shorter string was identical to the start of the
               longer string.  -2 or +2 is returned if there was a difference between characters
               within the strings.

                       int     bytes_cmp_utf8(const U8 *b, STRLEN blen,
                                              const U8 *u, STRLEN ulen)

       bytes_from_utf8
               NOTE: this function is experimental and may change or be removed without notice.

               Converts a string "s" of length "len" from UTF-8 into native byte encoding.
               Unlike "utf8_to_bytes" but like "bytes_to_utf8", returns a pointer to the newly-
               created string, and updates "len" to contain the new length.  Returns the original
               string if no conversion occurs, "len" is unchanged.  Do nothing if "is_utf8"
               points to 0.  Sets "is_utf8" to 0 if "s" is converted or consisted entirely of
               characters that are invariant in UTF-8 (i.e., US-ASCII on non-EBCDIC machines).

                       U8*     bytes_from_utf8(const U8 *s, STRLEN *len,
                                               bool *is_utf8)

       bytes_to_utf8
               NOTE: this function is experimental and may change or be removed without notice.

               Converts a string "s" of length "len" bytes from the native encoding into UTF-8.
               Returns a pointer to the newly-created string, and sets "len" to reflect the new
               length in bytes.

               A "NUL" character will be written after the end of the string.

               If you want to convert to UTF-8 from encodings other than the native (Latin1 or
               EBCDIC), see "sv_recode_to_utf8"().

                       U8*     bytes_to_utf8(const U8 *s, STRLEN *len)

       DO_UTF8 Returns a bool giving whether or not the PV in "sv" is to be treated as being
               encoded in UTF-8.

               You should use this after a call to "SvPV()" or one of its variants, in case any
               call to string overloading updates the internal UTF-8 encoding flag.

                       bool    DO_UTF8(SV* sv)

       foldEQ_utf8
               Returns true if the leading portions of the strings "s1" and "s2" (either or both
               of which may be in UTF-8) are the same case-insensitively; false otherwise.  How
               far into the strings to compare is determined by other input parameters.

               If "u1" is true, the string "s1" is assumed to be in UTF-8-encoded Unicode;
               otherwise it is assumed to be in native 8-bit encoding.  Correspondingly for "u2"
               with respect to "s2".

               If the byte length "l1" is non-zero, it says how far into "s1" to check for fold
               equality.  In other words, "s1"+"l1" will be used as a goal to reach.  The scan
               will not be considered to be a match unless the goal is reached, and scanning
               won't continue past that goal.  Correspondingly for "l2" with respect to "s2".

               If "pe1" is non-"NULL" and the pointer it points to is not "NULL", that pointer is
               considered an end pointer to the position 1 byte past the maximum point in "s1"
               beyond which scanning will not continue under any circumstances.  (This routine
               assumes that UTF-8 encoded input strings are not malformed; malformed input can
               cause it to read past "pe1").  This means that if both "l1" and "pe1" are
               specified, and "pe1" is less than "s1"+"l1", the match will never be successful
               because it can never get as far as its goal (and in fact is asserted against).
               Correspondingly for "pe2" with respect to "s2".

               At least one of "s1" and "s2" must have a goal (at least one of "l1" and "l2" must
               be non-zero), and if both do, both have to be reached for a successful match.
               Also, if the fold of a character is multiple characters, all of them must be
               matched (see tr21 reference below for 'folding').

               Upon a successful match, if "pe1" is non-"NULL", it will be set to point to the
               beginning of the next character of "s1" beyond what was matched.  Correspondingly
               for "pe2" and "s2".

               For case-insensitiveness, the "casefolding" of Unicode is used instead of
               upper/lowercasing both the characters, see
               <http://www.unicode.org/unicode/reports/tr21/> (Case Mappings).

                       I32     foldEQ_utf8(const char *s1, char **pe1, UV l1,
                                           bool u1, const char *s2, char **pe2,
                                           UV l2, bool u2)

       is_ascii_string
               This is a misleadingly-named synonym for "is_utf8_invariant_string".  On ASCII-ish
               platforms, the name isn't misleading: the ASCII-range characters are exactly the
               UTF-8 invariants.  But EBCDIC machines have more invariants than just the ASCII
               characters, so "is_utf8_invariant_string" is preferred.

                       bool    is_ascii_string(const U8* const s,
                                               const STRLEN len)

       is_c9strict_utf8_string
               Returns TRUE if the first "len" bytes of string "s" form a valid UTF-8-encoded
               string that conforms to Unicode Corrigendum #9
               <http://www.unicode.org/versions/corrigendum9.html>; otherwise it returns FALSE.
               If "len" is 0, it will be calculated using strlen(s) (which means if you use this
               option, that "s" can't have embedded "NUL" characters and has to have a
               terminating "NUL" byte).  Note that all characters being ASCII constitute 'a valid
               UTF-8 string'.

               This function returns FALSE for strings containing any code points above the
               Unicode max of 0x10FFFF or surrogate code points, but accepts non-character code
               points per Corrigendum #9 <http://www.unicode.org/versions/corrigendum9.html>.

               See also "is_utf8_invariant_string", "is_utf8_string", "is_utf8_string_flags",
               "is_utf8_string_loc", "is_utf8_string_loc_flags", "is_utf8_string_loclen",
               "is_utf8_string_loclen_flags", "is_utf8_fixed_width_buf_flags",
               "is_utf8_fixed_width_buf_loc_flags", "is_utf8_fixed_width_buf_loclen_flags",
               "is_strict_utf8_string", "is_strict_utf8_string_loc",
               "is_strict_utf8_string_loclen", "is_c9strict_utf8_string_loc", and
               "is_c9strict_utf8_string_loclen".

                       bool    is_c9strict_utf8_string(const U8 *s,
                                                       const STRLEN len)

       is_c9strict_utf8_string_loc
               Like "is_c9strict_utf8_string" but stores the location of the failure (in the case
               of "utf8ness failure") or the location "s"+"len" (in the case of "utf8ness
               success") in the "ep" pointer.

               See also "is_c9strict_utf8_string_loclen".

                       bool    is_c9strict_utf8_string_loc(const U8 *s,
                                                           const STRLEN len,
                                                           const U8 **ep)

       is_c9strict_utf8_string_loclen
               Like "is_c9strict_utf8_string" but stores the location of the failure (in the case
               of "utf8ness failure") or the location "s"+"len" (in the case of "utf8ness
               success") in the "ep" pointer, and the number of UTF-8 encoded characters in the
               "el" pointer.

               See also "is_c9strict_utf8_string_loc".

                       bool    is_c9strict_utf8_string_loclen(
                                   const U8 *s, const STRLEN len,
                                   const U8 **ep, STRLEN *el
                               )

       isC9_STRICT_UTF8_CHAR
               Evaluates to non-zero if the first few bytes of the string starting at "s" and
               looking no further than "e - 1" are well-formed UTF-8 that represents some Unicode
               non-surrogate code point; otherwise it evaluates to 0.  If non-zero, the value
               gives how many bytes starting at "s" comprise the code point's representation.
               Any bytes remaining before "e", but beyond the ones needed to form the first code
               point in "s", are not examined.

               The largest acceptable code point is the Unicode maximum 0x10FFFF.  This differs
               from "isSTRICT_UTF8_CHAR" only in that it accepts non-character code points.  This
               corresponds to Unicode Corrigendum #9
               <http://www.unicode.org/versions/corrigendum9.html>.  which said that non-
               character code points are merely discouraged rather than completely forbidden in
               open interchange.  See "Noncharacter code points" in perlunicode.

               Use "isUTF8_CHAR" to check for Perl's extended UTF-8; and "isUTF8_CHAR_flags" for
               a more customized definition.

               Use "is_c9strict_utf8_string", "is_c9strict_utf8_string_loc", and
               "is_c9strict_utf8_string_loclen" to check entire strings.

                       STRLEN  isC9_STRICT_UTF8_CHAR(const U8 *s, const U8 *e)

       is_invariant_string
               This is a somewhat misleadingly-named synonym for "is_utf8_invariant_string".
               "is_utf8_invariant_string" is preferred, as it indicates under what conditions the
               string is invariant.

                       bool    is_invariant_string(const U8* const s,
                                                   const STRLEN len)

       isSTRICT_UTF8_CHAR
               Evaluates to non-zero if the first few bytes of the string starting at "s" and
               looking no further than "e - 1" are well-formed UTF-8 that represents some Unicode
               code point completely acceptable for open interchange between all applications;
               otherwise it evaluates to 0.  If non-zero, the value gives how many bytes starting
               at "s" comprise the code point's representation.  Any bytes remaining before "e",
               but beyond the ones needed to form the first code point in "s", are not examined.

               The largest acceptable code point is the Unicode maximum 0x10FFFF, and must not be
               a surrogate nor a non-character code point.  Thus this excludes any code point
               from Perl's extended UTF-8.

               This is used to efficiently decide if the next few bytes in "s" is legal Unicode-
               acceptable UTF-8 for a single character.

               Use "isC9_STRICT_UTF8_CHAR" to use the Unicode Corrigendum #9
               <http://www.unicode.org/versions/corrigendum9.html> definition of allowable code
               points; "isUTF8_CHAR" to check for Perl's extended UTF-8; and "isUTF8_CHAR_flags"
               for a more customized definition.

               Use "is_strict_utf8_string", "is_strict_utf8_string_loc", and
               "is_strict_utf8_string_loclen" to check entire strings.

                       STRLEN  isSTRICT_UTF8_CHAR(const U8 *s, const U8 *e)

       is_strict_utf8_string
               Returns TRUE if the first "len" bytes of string "s" form a valid UTF-8-encoded
               string that is fully interchangeable by any application using Unicode rules;
               otherwise it returns FALSE.  If "len" is 0, it will be calculated using strlen(s)
               (which means if you use this option, that "s" can't have embedded "NUL" characters
               and has to have a terminating "NUL" byte).  Note that all characters being ASCII
               constitute 'a valid UTF-8 string'.

               This function returns FALSE for strings containing any code points above the
               Unicode max of 0x10FFFF, surrogate code points, or non-character code points.

               See also "is_utf8_invariant_string", "is_utf8_string", "is_utf8_string_flags",
               "is_utf8_string_loc", "is_utf8_string_loc_flags", "is_utf8_string_loclen",
               "is_utf8_string_loclen_flags", "is_utf8_fixed_width_buf_flags",
               "is_utf8_fixed_width_buf_loc_flags", "is_utf8_fixed_width_buf_loclen_flags",
               "is_strict_utf8_string_loc", "is_strict_utf8_string_loclen",
               "is_c9strict_utf8_string", "is_c9strict_utf8_string_loc", and
               "is_c9strict_utf8_string_loclen".

                       bool    is_strict_utf8_string(const U8 *s,
                                                     const STRLEN len)

       is_strict_utf8_string_loc
               Like "is_strict_utf8_string" but stores the location of the failure (in the case
               of "utf8ness failure") or the location "s"+"len" (in the case of "utf8ness
               success") in the "ep" pointer.

               See also "is_strict_utf8_string_loclen".

                       bool    is_strict_utf8_string_loc(const U8 *s,
                                                         const STRLEN len,
                                                         const U8 **ep)

       is_strict_utf8_string_loclen
               Like "is_strict_utf8_string" but stores the location of the failure (in the case
               of "utf8ness failure") or the location "s"+"len" (in the case of "utf8ness
               success") in the "ep" pointer, and the number of UTF-8 encoded characters in the
               "el" pointer.

               See also "is_strict_utf8_string_loc".

                       bool    is_strict_utf8_string_loclen(const U8 *s,
                                                            const STRLEN len,
                                                            const U8 **ep,
                                                            STRLEN *el)

       is_utf8_fixed_width_buf_flags
               Returns TRUE if the fixed-width buffer starting at "s" with length "len" is
               entirely valid UTF-8, subject to the restrictions given by "flags"; otherwise it
               returns FALSE.

               If "flags" is 0, any well-formed UTF-8, as extended by Perl, is accepted without
               restriction.  If the final few bytes of the buffer do not form a complete code
               point, this will return TRUE anyway, provided that
               "is_utf8_valid_partial_char_flags" returns TRUE for them.

               If "flags" in non-zero, it can be any combination of the "UTF8_DISALLOW_foo" flags
               accepted by "utf8n_to_uvchr", and with the same meanings.

               This function differs from "is_utf8_string_flags" only in that the latter returns
               FALSE if the final few bytes of the string don't form a complete code point.

                       bool    is_utf8_fixed_width_buf_flags(
                                   const U8 * const s, const STRLEN len,
                                   const U32 flags
                               )

       is_utf8_fixed_width_buf_loclen_flags
               Like "is_utf8_fixed_width_buf_loc_flags" but stores the number of complete, valid
               characters found in the "el" pointer.

                       bool    is_utf8_fixed_width_buf_loclen_flags(
                                   const U8 * const s, const STRLEN len,
                                   const U8 **ep, STRLEN *el, const U32 flags
                               )

       is_utf8_fixed_width_buf_loc_flags
               Like "is_utf8_fixed_width_buf_flags" but stores the location of the failure in the
               "ep" pointer.  If the function returns TRUE, *ep will point to the beginning of
               any partial character at the end of the buffer; if there is no partial character
               *ep will contain "s"+"len".

               See also "is_utf8_fixed_width_buf_loclen_flags".

                       bool    is_utf8_fixed_width_buf_loc_flags(
                                   const U8 * const s, const STRLEN len,
                                   const U8 **ep, const U32 flags
                               )

       is_utf8_invariant_string
               Returns TRUE if the first "len" bytes of the string "s" are the same regardless of
               the UTF-8 encoding of the string (or UTF-EBCDIC encoding on EBCDIC machines);
               otherwise it returns FALSE.  That is, it returns TRUE if they are UTF-8 invariant.
               On ASCII-ish machines, all the ASCII characters and only the ASCII characters fit
               this definition.  On EBCDIC machines, the ASCII-range characters are invariant,
               but so also are the C1 controls.

               If "len" is 0, it will be calculated using strlen(s), (which means if you use this
               option, that "s" can't have embedded "NUL" characters and has to have a
               terminating "NUL" byte).

               See also "is_utf8_string", "is_utf8_string_flags", "is_utf8_string_loc",
               "is_utf8_string_loc_flags", "is_utf8_string_loclen",
               "is_utf8_string_loclen_flags", "is_utf8_fixed_width_buf_flags",
               "is_utf8_fixed_width_buf_loc_flags", "is_utf8_fixed_width_buf_loclen_flags",
               "is_strict_utf8_string", "is_strict_utf8_string_loc",
               "is_strict_utf8_string_loclen", "is_c9strict_utf8_string",
               "is_c9strict_utf8_string_loc", and "is_c9strict_utf8_string_loclen".

                       bool    is_utf8_invariant_string(const U8* const s,
                                                        STRLEN const len)

       is_utf8_string
               Returns TRUE if the first "len" bytes of string "s" form a valid
               Perl-extended-UTF-8 string; returns FALSE otherwise.  If "len" is 0, it will be
               calculated using strlen(s) (which means if you use this option, that "s" can't
               have embedded "NUL" characters and has to have a terminating "NUL" byte).  Note
               that all characters being ASCII constitute 'a valid UTF-8 string'.

               This function considers Perl's extended UTF-8 to be valid.  That means that code
               points above Unicode, surrogates, and non-character code points are considered
               valid by this function.  Use "is_strict_utf8_string", "is_c9strict_utf8_string",
               or "is_utf8_string_flags" to restrict what code points are considered valid.

               See also "is_utf8_invariant_string", "is_utf8_string_loc",
               "is_utf8_string_loclen", "is_utf8_fixed_width_buf_flags",
               "is_utf8_fixed_width_buf_loc_flags", "is_utf8_fixed_width_buf_loclen_flags",

                       bool    is_utf8_string(const U8 *s, const STRLEN len)

       is_utf8_string_flags
               Returns TRUE if the first "len" bytes of string "s" form a valid UTF-8 string,
               subject to the restrictions imposed by "flags"; returns FALSE otherwise.  If "len"
               is 0, it will be calculated using strlen(s) (which means if you use this option,
               that "s" can't have embedded "NUL" characters and has to have a terminating "NUL"
               byte).  Note that all characters being ASCII constitute 'a valid UTF-8 string'.

               If "flags" is 0, this gives the same results as "is_utf8_string"; if "flags" is
               "UTF8_DISALLOW_ILLEGAL_INTERCHANGE", this gives the same results as
               "is_strict_utf8_string"; and if "flags" is "UTF8_DISALLOW_ILLEGAL_C9_INTERCHANGE",
               this gives the same results as "is_c9strict_utf8_string".  Otherwise "flags" may
               be any combination of the "UTF8_DISALLOW_foo" flags understood by
               "utf8n_to_uvchr", with the same meanings.

               See also "is_utf8_invariant_string", "is_utf8_string", "is_utf8_string_loc",
               "is_utf8_string_loc_flags", "is_utf8_string_loclen",
               "is_utf8_string_loclen_flags", "is_utf8_fixed_width_buf_flags",
               "is_utf8_fixed_width_buf_loc_flags", "is_utf8_fixed_width_buf_loclen_flags",
               "is_strict_utf8_string", "is_strict_utf8_string_loc",
               "is_strict_utf8_string_loclen", "is_c9strict_utf8_string",
               "is_c9strict_utf8_string_loc", and "is_c9strict_utf8_string_loclen".

                       bool    is_utf8_string_flags(const U8 *s,
                                                    const STRLEN len,
                                                    const U32 flags)

       is_utf8_string_loc
               Like "is_utf8_string" but stores the location of the failure (in the case of
               "utf8ness failure") or the location "s"+"len" (in the case of "utf8ness success")
               in the "ep" pointer.

               See also "is_utf8_string_loclen".

                       bool    is_utf8_string_loc(const U8 *s,
                                                  const STRLEN len,
                                                  const U8 **ep)

       is_utf8_string_loclen
               Like "is_utf8_string" but stores the location of the failure (in the case of
               "utf8ness failure") or the location "s"+"len" (in the case of "utf8ness success")
               in the "ep" pointer, and the number of UTF-8 encoded characters in the "el"
               pointer.

               See also "is_utf8_string_loc".

                       bool    is_utf8_string_loclen(const U8 *s,
                                                     const STRLEN len,
                                                     const U8 **ep, STRLEN *el)

       is_utf8_string_loclen_flags
               Like "is_utf8_string_flags" but stores the location of the failure (in the case of
               "utf8ness failure") or the location "s"+"len" (in the case of "utf8ness success")
               in the "ep" pointer, and the number of UTF-8 encoded characters in the "el"
               pointer.

               See also "is_utf8_string_loc_flags".

                       bool    is_utf8_string_loclen_flags(const U8 *s,
                                                           const STRLEN len,
                                                           const U8 **ep,
                                                           STRLEN *el,
                                                           const U32 flags)

       is_utf8_string_loc_flags
               Like "is_utf8_string_flags" but stores the location of the failure (in the case of
               "utf8ness failure") or the location "s"+"len" (in the case of "utf8ness success")
               in the "ep" pointer.

               See also "is_utf8_string_loclen_flags".

                       bool    is_utf8_string_loc_flags(const U8 *s,
                                                        const STRLEN len,
                                                        const U8 **ep,
                                                        const U32 flags)

       is_utf8_valid_partial_char
               Returns 0 if the sequence of bytes starting at "s" and looking no further than
               "e - 1" is the UTF-8 encoding, as extended by Perl, for one or more code points.
               Otherwise, it returns 1 if there exists at least one non-empty sequence of bytes
               that when appended to sequence "s", starting at position "e" causes the entire
               sequence to be the well-formed UTF-8 of some code point; otherwise returns 0.

               In other words this returns TRUE if "s" points to a partial UTF-8-encoded code
               point.

               This is useful when a fixed-length buffer is being tested for being well-formed
               UTF-8, but the final few bytes in it don't comprise a full character; that is, it
               is split somewhere in the middle of the final code point's UTF-8 representation.
               (Presumably when the buffer is refreshed with the next chunk of data, the new
               first bytes will complete the partial code point.)   This function is used to
               verify that the final bytes in the current buffer are in fact the legal beginning
               of some code point, so that if they aren't, the failure can be signalled without
               having to wait for the next read.

                       bool    is_utf8_valid_partial_char(const U8 * const s,
                                                          const U8 * const e)

       is_utf8_valid_partial_char_flags
               Like "is_utf8_valid_partial_char", it returns a boolean giving whether or not the
               input is a valid UTF-8 encoded partial character, but it takes an extra parameter,
               "flags", which can further restrict which code points are considered valid.

               If "flags" is 0, this behaves identically to "is_utf8_valid_partial_char".
               Otherwise "flags" can be any combination of the "UTF8_DISALLOW_foo" flags accepted
               by "utf8n_to_uvchr".  If there is any sequence of bytes that can complete the
               input partial character in such a way that a non-prohibited character is formed,
               the function returns TRUE; otherwise FALSE.  Non character code points cannot be
               determined based on partial character input.  But many  of the other possible
               excluded types can be determined from just the first one or two bytes.

                       bool    is_utf8_valid_partial_char_flags(
                                   const U8 * const s, const U8 * const e,
                                   const U32 flags
                               )

       isUTF8_CHAR
               Evaluates to non-zero if the first few bytes of the string starting at "s" and
               looking no further than "e - 1" are well-formed UTF-8, as extended by Perl, that
               represents some code point; otherwise it evaluates to 0.  If non-zero, the value
               gives how many bytes starting at "s" comprise the code point's representation.
               Any bytes remaining before "e", but beyond the ones needed to form the first code
               point in "s", are not examined.

               The code point can be any that will fit in a UV on this machine, using Perl's
               extension to official UTF-8 to represent those higher than the Unicode maximum of
               0x10FFFF.  That means that this macro is used to efficiently decide if the next
               few bytes in "s" is legal UTF-8 for a single character.

               Use "isSTRICT_UTF8_CHAR" to restrict the acceptable code points to those defined
               by Unicode to be fully interchangeable across applications;
               "isC9_STRICT_UTF8_CHAR" to use the Unicode Corrigendum #9
               <http://www.unicode.org/versions/corrigendum9.html> definition of allowable code
               points; and "isUTF8_CHAR_flags" for a more customized definition.

               Use "is_utf8_string", "is_utf8_string_loc", and "is_utf8_string_loclen" to check
               entire strings.

               Note that it is deprecated to use code points higher than what will fit in an IV.
               This macro does not raise any warnings for such code points, treating them as
               valid.

               Note also that a UTF-8 INVARIANT character (i.e. ASCII on non-EBCDIC machines) is
               a valid UTF-8 character.

                       STRLEN  isUTF8_CHAR(const U8 *s, const U8 *e)

       isUTF8_CHAR_flags
               Evaluates to non-zero if the first few bytes of the string starting at "s" and
               looking no further than "e - 1" are well-formed UTF-8, as extended by Perl, that
               represents some code point, subject to the restrictions given by "flags";
               otherwise it evaluates to 0.  If non-zero, the value gives how many bytes starting
               at "s" comprise the code point's representation.  Any bytes remaining before "e",
               but beyond the ones needed to form the first code point in "s", are not examined.

               If "flags" is 0, this gives the same results as "isUTF8_CHAR"; if "flags" is
               "UTF8_DISALLOW_ILLEGAL_INTERCHANGE", this gives the same results as
               "isSTRICT_UTF8_CHAR"; and if "flags" is "UTF8_DISALLOW_ILLEGAL_C9_INTERCHANGE",
               this gives the same results as "isC9_STRICT_UTF8_CHAR".  Otherwise "flags" may be
               any combination of the "UTF8_DISALLOW_foo" flags understood by "utf8n_to_uvchr",
               with the same meanings.

               The three alternative macros are for the most commonly needed validations; they
               are likely to run somewhat faster than this more general one, as they can be
               inlined into your code.

               Use "is_utf8_string_flags", "is_utf8_string_loc_flags", and
               "is_utf8_string_loclen_flags" to check entire strings.

                       STRLEN  isUTF8_CHAR_flags(const U8 *s, const U8 *e,
                                                  const U32 flags)

       pv_uni_display
               Build to the scalar "dsv" a displayable version of the string "spv", length "len",
               the displayable version being at most "pvlim" bytes long (if longer, the rest is
               truncated and "..." will be appended).

               The "flags" argument can have "UNI_DISPLAY_ISPRINT" set to display "isPRINT()"able
               characters as themselves, "UNI_DISPLAY_BACKSLASH" to display the "\\[nrfta\\]" as
               the backslashed versions (like "\n") ("UNI_DISPLAY_BACKSLASH" is preferred over
               "UNI_DISPLAY_ISPRINT" for "\\").  "UNI_DISPLAY_QQ" (and its alias
               "UNI_DISPLAY_REGEX") have both "UNI_DISPLAY_BACKSLASH" and "UNI_DISPLAY_ISPRINT"
               turned on.

               The pointer to the PV of the "dsv" is returned.

               See also "sv_uni_display".

                       char*   pv_uni_display(SV *dsv, const U8 *spv,
                                              STRLEN len, STRLEN pvlim,
                                              UV flags)

       REPLACEMENT_CHARACTER_UTF8
               This is a macro that evaluates to a string constant of the  UTF-8 bytes that
               define the Unicode REPLACEMENT CHARACTER (U+FFFD) for the platform that perl is
               compiled on.  This allows code to use a mnemonic for this character that works on
               both ASCII and EBCDIC platforms.  "sizeof(REPLACEMENT_CHARACTER_UTF8) - 1" can be
               used to get its length in bytes.

       sv_cat_decode
               "encoding" is assumed to be an "Encode" object, the PV of "ssv" is assumed to be
               octets in that encoding and decoding the input starts from the position which
               "(PV + *offset)" pointed to.  "dsv" will be concatenated with the decoded UTF-8
               string from "ssv".  Decoding will terminate when the string "tstr" appears in
               decoding output or the input ends on the PV of "ssv".  The value which "offset"
               points will be modified to the last input position on "ssv".

               Returns TRUE if the terminator was found, else returns FALSE.

                       bool    sv_cat_decode(SV* dsv, SV *encoding, SV *ssv,
                                             int *offset, char* tstr, int tlen)

       sv_recode_to_utf8
               "encoding" is assumed to be an "Encode" object, on entry the PV of "sv" is assumed
               to be octets in that encoding, and "sv" will be converted into Unicode (and
               UTF-8).

               If "sv" already is UTF-8 (or if it is not "POK"), or if "encoding" is not a
               reference, nothing is done to "sv".  If "encoding" is not an "Encode::XS" Encoding
               object, bad things will happen.  (See cpan/Encode/encoding.pm and Encode.)

               The PV of "sv" is returned.

                       char*   sv_recode_to_utf8(SV* sv, SV *encoding)

       sv_uni_display
               Build to the scalar "dsv" a displayable version of the scalar "sv", the
               displayable version being at most "pvlim" bytes long (if longer, the rest is
               truncated and "..." will be appended).

               The "flags" argument is as in "pv_uni_display"().

               The pointer to the PV of the "dsv" is returned.

                       char*   sv_uni_display(SV *dsv, SV *ssv, STRLEN pvlim,
                                              UV flags)

       to_utf8_case
               DEPRECATED!  It is planned to remove this function from a future release of Perl.
               Do not use it for new code; remove it from existing code.

               Instead use the appropriate one of "toUPPER_utf8_safe", "toTITLE_utf8_safe",
               "toLOWER_utf8_safe", or "toFOLD_utf8_safe".

               This function will be removed in Perl v5.28.

               "p" contains the pointer to the UTF-8 string encoding the character that is being
               converted.  This routine assumes that the character at "p" is well-formed.

               "ustrp" is a pointer to the character buffer to put the conversion result to.
               "lenp" is a pointer to the length of the result.

               "swashp" is a pointer to the swash to use.

               Both the special and normal mappings are stored in lib/unicore/To/Foo.pl, and
               loaded by "SWASHNEW", using lib/utf8_heavy.pl.  "special" (usually, but not
               always, a multicharacter mapping), is tried first.

               "special" is a string, normally "NULL" or "".  "NULL" means to not use any special
               mappings; "" means to use the special mappings.  Values other than these two are
               treated as the name of the hash containing the special mappings, like
               "utf8::ToSpecLower".

               "normal" is a string like "ToLower" which means the swash %utf8::ToLower.

               Code points above the platform's "IV_MAX" will raise a deprecation warning, unless
               those are turned off.

                       UV      to_utf8_case(const U8 *p, U8* ustrp,
                                            STRLEN *lenp, SV **swashp,
                                            const char *normal,
                                            const char *special)

       to_utf8_fold
               DEPRECATED!  It is planned to remove this function from a future release of Perl.
               Do not use it for new code; remove it from existing code.

               Instead use "toFOLD_utf8_safe".

                       UV      to_utf8_fold(const U8 *p, U8* ustrp,
                                            STRLEN *lenp)

       to_utf8_lower
               DEPRECATED!  It is planned to remove this function from a future release of Perl.
               Do not use it for new code; remove it from existing code.

               Instead use "toLOWER_utf8_safe".

                       UV      to_utf8_lower(const U8 *p, U8* ustrp,
                                             STRLEN *lenp)

       to_utf8_title
               DEPRECATED!  It is planned to remove this function from a future release of Perl.
               Do not use it for new code; remove it from existing code.

               Instead use "toTITLE_utf8_safe".

                       UV      to_utf8_title(const U8 *p, U8* ustrp,
                                             STRLEN *lenp)

       to_utf8_upper
               DEPRECATED!  It is planned to remove this function from a future release of Perl.
               Do not use it for new code; remove it from existing code.

               Instead use "toUPPER_utf8_safe".

                       UV      to_utf8_upper(const U8 *p, U8* ustrp,
                                             STRLEN *lenp)

       utf8n_to_uvchr
               THIS FUNCTION SHOULD BE USED IN ONLY VERY SPECIALIZED CIRCUMSTANCES.  Most code
               should use "utf8_to_uvchr_buf"() rather than call this directly.

               Bottom level UTF-8 decode routine.  Returns the native code point value of the
               first character in the string "s", which is assumed to be in UTF-8 (or UTF-EBCDIC)
               encoding, and no longer than "curlen" bytes; *retlen (if "retlen" isn't NULL) will
               be set to the length, in bytes, of that character.

               The value of "flags" determines the behavior when "s" does not point to a well-
               formed UTF-8 character.  If "flags" is 0, encountering a malformation causes zero
               to be returned and *retlen is set so that ("s" + *retlen) is the next possible
               position in "s" that could begin a non-malformed character.  Also, if UTF-8
               warnings haven't been lexically disabled, a warning is raised.  Some UTF-8 input
               sequences may contain multiple malformations.  This function tries to find every
               possible one in each call, so multiple warnings can be raised for each sequence.

               Various ALLOW flags can be set in "flags" to allow (and not warn on) individual
               types of malformations, such as the sequence being overlong (that is, when there
               is a shorter sequence that can express the same code point; overlong sequences are
               expressly forbidden in the UTF-8 standard due to potential security issues).
               Another malformation example is the first byte of a character not being a legal
               first byte.  See utf8.h for the list of such flags.  Even if allowed, this
               function generally returns the Unicode REPLACEMENT CHARACTER when it encounters a
               malformation.  There are flags in utf8.h to override this behavior for the
               overlong malformations, but don't do that except for very specialized purposes.

               The "UTF8_CHECK_ONLY" flag overrides the behavior when a non-allowed (by other
               flags) malformation is found.  If this flag is set, the routine assumes that the
               caller will raise a warning, and this function will silently just set "retlen" to
               "-1" (cast to "STRLEN") and return zero.

               Note that this API requires disambiguation between successful decoding a "NUL"
               character, and an error return (unless the "UTF8_CHECK_ONLY" flag is set), as in
               both cases, 0 is returned, and, depending on the malformation, "retlen" may be set
               to 1.  To disambiguate, upon a zero return, see if the first byte of "s" is 0 as
               well.  If so, the input was a "NUL"; if not, the input had an error.  Or you can
               use "utf8n_to_uvchr_error".

               Certain code points are considered problematic.  These are Unicode surrogates,
               Unicode non-characters, and code points above the Unicode maximum of 0x10FFFF.  By
               default these are considered regular code points, but certain situations warrant
               special handling for them, which can be specified using the "flags" parameter.  If
               "flags" contains "UTF8_DISALLOW_ILLEGAL_INTERCHANGE", all three classes are
               treated as malformations and handled as such.  The flags
               "UTF8_DISALLOW_SURROGATE", "UTF8_DISALLOW_NONCHAR", and "UTF8_DISALLOW_SUPER"
               (meaning above the legal Unicode maximum) can be set to disallow these categories
               individually.  "UTF8_DISALLOW_ILLEGAL_INTERCHANGE" restricts the allowed inputs to
               the strict UTF-8 traditionally defined by Unicode.  Use
               "UTF8_DISALLOW_ILLEGAL_C9_INTERCHANGE" to use the strictness definition given by
               Unicode Corrigendum #9 <http://www.unicode.org/versions/corrigendum9.html>.  The
               difference between traditional strictness and C9 strictness is that the latter
               does not forbid non-character code points.  (They are still discouraged, however.)
               For more discussion see "Noncharacter code points" in perlunicode.

               The flags "UTF8_WARN_ILLEGAL_INTERCHANGE", "UTF8_WARN_ILLEGAL_C9_INTERCHANGE",
               "UTF8_WARN_SURROGATE", "UTF8_WARN_NONCHAR", and "UTF8_WARN_SUPER" will cause
               warning messages to be raised for their respective categories, but otherwise the
               code points are considered valid (not malformations).  To get a category to both
               be treated as a malformation and raise a warning, specify both the WARN and
               DISALLOW flags.  (But note that warnings are not raised if lexically disabled nor
               if "UTF8_CHECK_ONLY" is also specified.)

               It is now deprecated to have very high code points (above "IV_MAX" on the
               platforms) and this function will raise a deprecation warning for these (unless
               such warnings are turned off).  This value is typically 0x7FFF_FFFF (2**31 -1) in
               a 32-bit word.

               Code points above 0x7FFF_FFFF (2**31 - 1) were never specified in any standard, so
               using them is more problematic than other above-Unicode code points.  Perl
               invented an extension to UTF-8 to represent the ones above 2**36-1, so it is
               likely that non-Perl languages will not be able to read files that contain these;
               nor would Perl understand files written by something that uses a different
               extension.  For these reasons, there is a separate set of flags that can warn
               and/or disallow these extremely high code points, even if other above-Unicode ones
               are accepted.  These are the "UTF8_WARN_ABOVE_31_BIT" and
               "UTF8_DISALLOW_ABOVE_31_BIT" flags.  These are entirely independent from the
               deprecation warning for code points above "IV_MAX".  On 32-bit machines, it will
               eventually be forbidden to have any code point that needs more than 31 bits to
               represent.  When that happens, effectively the "UTF8_DISALLOW_ABOVE_31_BIT" flag
               will always be set on 32-bit machines.  (Of course "UTF8_DISALLOW_SUPER" will
               treat all above-Unicode code points, including these, as malformations; and
               "UTF8_WARN_SUPER" warns on these.)

               On EBCDIC platforms starting in Perl v5.24, the Perl extension for representing
               extremely high code points kicks in at 0x3FFF_FFFF (2**30 -1), which is lower than
               on ASCII.  Prior to that, code points 2**31 and higher were simply
               unrepresentable, and a different, incompatible method was used to represent code
               points between 2**30 and 2**31 - 1.  The flags "UTF8_WARN_ABOVE_31_BIT" and
               "UTF8_DISALLOW_ABOVE_31_BIT" have the same function as on ASCII platforms, warning
               and disallowing 2**31 and higher.

               All other code points corresponding to Unicode characters, including private use
               and those yet to be assigned, are never considered malformed and never warn.

                       UV      utf8n_to_uvchr(const U8 *s, STRLEN curlen,
                                              STRLEN *retlen, const U32 flags)

       utf8n_to_uvchr_error
               THIS FUNCTION SHOULD BE USED IN ONLY VERY SPECIALIZED CIRCUMSTANCES.  Most code
               should use "utf8_to_uvchr_buf"() rather than call this directly.

               This function is for code that needs to know what the precise malformation(s) are
               when an error is found.

               It is like "utf8n_to_uvchr" but it takes an extra parameter placed after all the
               others, "errors".  If this parameter is 0, this function behaves identically to
               "utf8n_to_uvchr".  Otherwise, "errors" should be a pointer to a "U32" variable,
               which this function sets to indicate any errors found.  Upon return, if *errors is
               0, there were no errors found.  Otherwise, *errors is the bit-wise "OR" of the
               bits described in the list below.  Some of these bits will be set if a
               malformation is found, even if the input "flags" parameter indicates that the
               given malformation is allowed; those exceptions are noted:

               "UTF8_GOT_ABOVE_31_BIT"
                   The code point represented by the input UTF-8 sequence occupies more than 31
                   bits.  This bit is set only if the input "flags" parameter contains either the
                   "UTF8_DISALLOW_ABOVE_31_BIT" or the "UTF8_WARN_ABOVE_31_BIT" flags.

               "UTF8_GOT_CONTINUATION"
                   The input sequence was malformed in that the first byte was a a UTF-8
                   continuation byte.

               "UTF8_GOT_EMPTY"
                   The input "curlen" parameter was 0.

               "UTF8_GOT_LONG"
                   The input sequence was malformed in that there is some other sequence that
                   evaluates to the same code point, but that sequence is shorter than this one.

               "UTF8_GOT_NONCHAR"
                   The code point represented by the input UTF-8 sequence is for a Unicode non-
                   character code point.  This bit is set only if the input "flags" parameter
                   contains either the "UTF8_DISALLOW_NONCHAR" or the "UTF8_WARN_NONCHAR" flags.

               "UTF8_GOT_NON_CONTINUATION"
                   The input sequence was malformed in that a non-continuation type byte was
                   found in a position where only a continuation type one should be.

               "UTF8_GOT_OVERFLOW"
                   The input sequence was malformed in that it is for a code point that is not
                   representable in the number of bits available in a UV on the current platform.

               "UTF8_GOT_SHORT"
                   The input sequence was malformed in that "curlen" is smaller than required for
                   a complete sequence.  In other words, the input is for a partial character
                   sequence.

               "UTF8_GOT_SUPER"
                   The input sequence was malformed in that it is for a non-Unicode code point;
                   that is, one above the legal Unicode maximum.  This bit is set only if the
                   input "flags" parameter contains either the "UTF8_DISALLOW_SUPER" or the
                   "UTF8_WARN_SUPER" flags.

               "UTF8_GOT_SURROGATE"
                   The input sequence was malformed in that it is for a -Unicode UTF-16 surrogate
                   code point.  This bit is set only if the input "flags" parameter contains
                   either the "UTF8_DISALLOW_SURROGATE" or the "UTF8_WARN_SURROGATE" flags.

               To do your own error handling, call this function with the "UTF8_CHECK_ONLY" flag
               to suppress any warnings, and then examine the *errors return.

                       UV      utf8n_to_uvchr_error(const U8 *s, STRLEN curlen,
                                                    STRLEN *retlen,
                                                    const U32 flags,
                                                    U32 * errors)

       utf8n_to_uvuni
               Instead use "utf8_to_uvchr_buf", or rarely, "utf8n_to_uvchr".

               This function was useful for code that wanted to handle both EBCDIC and ASCII
               platforms with Unicode properties, but starting in Perl v5.20, the distinctions
               between the platforms have mostly been made invisible to most code, so this
               function is quite unlikely to be what you want.  If you do need this precise
               functionality, use instead "NATIVE_TO_UNI(utf8_to_uvchr_buf(...))"  or
               "NATIVE_TO_UNI(utf8n_to_uvchr(...))".

                       UV      utf8n_to_uvuni(const U8 *s, STRLEN curlen,
                                              STRLEN *retlen, U32 flags)

       UTF8SKIP
               returns the number of bytes in the UTF-8 encoded character whose first (perhaps
               only) byte is pointed to by "s".

                       STRLEN  UTF8SKIP(char* s)

       utf8_distance
               Returns the number of UTF-8 characters between the UTF-8 pointers "a" and "b".

               WARNING: use only if you *know* that the pointers point inside the same UTF-8
               buffer.

                       IV      utf8_distance(const U8 *a, const U8 *b)

       utf8_hop
               Return the UTF-8 pointer "s" displaced by "off" characters, either forward or
               backward.

               WARNING: do not use the following unless you *know* "off" is within the UTF-8 data
               pointed to by "s" *and* that on entry "s" is aligned on the first byte of
               character or just after the last byte of a character.

                       U8*     utf8_hop(const U8 *s, SSize_t off)

       utf8_hop_back
               Return the UTF-8 pointer "s" displaced by up to "off" characters, backward.

               "off" must be non-positive.

               "s" must be after or equal to "start".

               When moving backward it will not move before "start".

               Will not exceed this limit even if the string is not valid "UTF-8".

                       U8*     utf8_hop_back(const U8 *s, SSize_t off,
                                             const U8 *start)

       utf8_hop_forward
               Return the UTF-8 pointer "s" displaced by up to "off" characters, forward.

               "off" must be non-negative.

               "s" must be before or equal to "end".

               When moving forward it will not move beyond "end".

               Will not exceed this limit even if the string is not valid "UTF-8".

                       U8*     utf8_hop_forward(const U8 *s, SSize_t off,
                                                const U8 *end)

       utf8_hop_safe
               Return the UTF-8 pointer "s" displaced by up to "off" characters, either forward
               or backward.

               When moving backward it will not move before "start".

               When moving forward it will not move beyond "end".

               Will not exceed those limits even if the string is not valid "UTF-8".

                       U8*     utf8_hop_safe(const U8 *s, SSize_t off,
                                             const U8 *start, const U8 *end)

       UTF8_IS_INVARIANT
               Evaluates to 1 if the byte "c" represents the same character when encoded in UTF-8
               as when not; otherwise evaluates to 0.  UTF-8 invariant characters can be copied
               as-is when converting to/from UTF-8, saving time.

               In spite of the name, this macro gives the correct result if the input string from
               which "c" comes is not encoded in UTF-8.

               See "UVCHR_IS_INVARIANT" for checking if a UV is invariant.

                       bool    UTF8_IS_INVARIANT(char c)

       UTF8_IS_NONCHAR
               Evaluates to non-zero if the first few bytes of the string starting at "s" and
               looking no further than "e - 1" are well-formed UTF-8 that represents one of the
               Unicode non-character code points; otherwise it evaluates to 0.  If non-zero, the
               value gives how many bytes starting at "s" comprise the code point's
               representation.

                       bool    UTF8_IS_NONCHAR(const U8 *s, const U8 *e)

       UTF8_IS_SUPER
               Recall that Perl recognizes an extension to UTF-8 that can encode code points
               larger than the ones defined by Unicode, which are 0..0x10FFFF.

               This macro evaluates to non-zero if the first few bytes of the string starting at
               "s" and looking no further than "e - 1" are from this UTF-8 extension; otherwise
               it evaluates to 0.  If non-zero, the value gives how many bytes starting at "s"
               comprise the code point's representation.

               0 is returned if the bytes are not well-formed extended UTF-8, or if they
               represent a code point that cannot fit in a UV on the current platform.  Hence
               this macro can give different results when run on a 64-bit word machine than on
               one with a 32-bit word size.

               Note that it is deprecated to have code points that are larger than what can fit
               in an IV on the current machine.

                       bool    UTF8_IS_SUPER(const U8 *s, const U8 *e)

       UTF8_IS_SURROGATE
               Evaluates to non-zero if the first few bytes of the string starting at "s" and
               looking no further than "e - 1" are well-formed UTF-8 that represents one of the
               Unicode surrogate code points; otherwise it evaluates to 0.  If non-zero, the
               value gives how many bytes starting at "s" comprise the code point's
               representation.

                       bool    UTF8_IS_SURROGATE(const U8 *s, const U8 *e)

       utf8_length
               Return the length of the UTF-8 char encoded string "s" in characters.  Stops at
               "e" (inclusive).  If "e < s" or if the scan would end up past "e", croaks.

                       STRLEN  utf8_length(const U8* s, const U8 *e)

       utf8_to_bytes
               NOTE: this function is experimental and may change or be removed without notice.

               Converts a string "s" of length "len" from UTF-8 into native byte encoding.
               Unlike "bytes_to_utf8", this over-writes the original string, and updates "len" to
               contain the new length.  Returns zero on failure, setting "len" to -1.

               If you need a copy of the string, see "bytes_from_utf8".

                       U8*     utf8_to_bytes(U8 *s, STRLEN *len)

       utf8_to_uvchr_buf
               Returns the native code point of the first character in the string "s" which is
               assumed to be in UTF-8 encoding; "send" points to 1 beyond the end of "s".
               *retlen will be set to the length, in bytes, of that character.

               If "s" does not point to a well-formed UTF-8 character and UTF8 warnings are
               enabled, zero is returned and *retlen is set (if "retlen" isn't "NULL") to -1.  If
               those warnings are off, the computed value, if well-defined (or the Unicode
               REPLACEMENT CHARACTER if not), is silently returned, and *retlen is set (if
               "retlen" isn't "NULL") so that ("s" + *retlen) is the next possible position in
               "s" that could begin a non-malformed character.  See "utf8n_to_uvchr" for details
               on when the REPLACEMENT CHARACTER is returned.

               Code points above the platform's "IV_MAX" will raise a deprecation warning, unless
               those are turned off.

                       UV      utf8_to_uvchr_buf(const U8 *s, const U8 *send,
                                                 STRLEN *retlen)

       utf8_to_uvuni_buf
               DEPRECATED!  It is planned to remove this function from a future release of Perl.
               Do not use it for new code; remove it from existing code.

               Only in very rare circumstances should code need to be dealing in Unicode (as
               opposed to native) code points.  In those few cases, use
               "NATIVE_TO_UNI(utf8_to_uvchr_buf(...))" instead.

               Returns the Unicode (not-native) code point of the first character in the string
               "s" which is assumed to be in UTF-8 encoding; "send" points to 1 beyond the end of
               "s".  "retlen" will be set to the length, in bytes, of that character.

               If "s" does not point to a well-formed UTF-8 character and UTF8 warnings are
               enabled, zero is returned and *retlen is set (if "retlen" isn't NULL) to -1.  If
               those warnings are off, the computed value if well-defined (or the Unicode
               REPLACEMENT CHARACTER, if not) is silently returned, and *retlen is set (if
               "retlen" isn't NULL) so that ("s" + *retlen) is the next possible position in "s"
               that could begin a non-malformed character.  See "utf8n_to_uvchr" for details on
               when the REPLACEMENT CHARACTER is returned.

               Code points above the platform's "IV_MAX" will raise a deprecation warning, unless
               those are turned off.

                       UV      utf8_to_uvuni_buf(const U8 *s, const U8 *send,
                                                 STRLEN *retlen)

       UVCHR_IS_INVARIANT
               Evaluates to 1 if the representation of code point "cp" is the same whether or not
               it is encoded in UTF-8; otherwise evaluates to 0.  UTF-8 invariant characters can
               be copied as-is when converting to/from UTF-8, saving time.  "cp" is Unicode if
               above 255; otherwise is platform-native.

                       bool    UVCHR_IS_INVARIANT(UV cp)

       UVCHR_SKIP
               returns the number of bytes required to represent the code point "cp" when encoded
               as UTF-8.  "cp" is a native (ASCII or EBCDIC) code point if less than 255; a
               Unicode code point otherwise.

                       STRLEN  UVCHR_SKIP(UV cp)

       uvchr_to_utf8
               Adds the UTF-8 representation of the native code point "uv" to the end of the
               string "d"; "d" should have at least "UVCHR_SKIP(uv)+1" (up to "UTF8_MAXBYTES+1")
               free bytes available.  The return value is the pointer to the byte after the end
               of the new character.  In other words,

                   d = uvchr_to_utf8(d, uv);

               is the recommended wide native character-aware way of saying

                   *(d++) = uv;

               This function accepts any UV as input, but very high code points (above "IV_MAX"
               on the platform)  will raise a deprecation warning.  This is typically 0x7FFF_FFFF
               in a 32-bit word.

               It is possible to forbid or warn on non-Unicode code points, or those that may be
               problematic by using "uvchr_to_utf8_flags".

                       U8*     uvchr_to_utf8(U8 *d, UV uv)

       uvchr_to_utf8_flags
               Adds the UTF-8 representation of the native code point "uv" to the end of the
               string "d"; "d" should have at least "UVCHR_SKIP(uv)+1" (up to "UTF8_MAXBYTES+1")
               free bytes available.  The return value is the pointer to the byte after the end
               of the new character.  In other words,

                   d = uvchr_to_utf8_flags(d, uv, flags);

               or, in most cases,

                   d = uvchr_to_utf8_flags(d, uv, 0);

               This is the Unicode-aware way of saying

                   *(d++) = uv;

               If "flags" is 0, this function accepts any UV as input, but very high code points
               (above "IV_MAX" for the platform)  will raise a deprecation warning.  This is
               typically 0x7FFF_FFFF in a 32-bit word.

               Specifying "flags" can further restrict what is allowed and not warned on, as
               follows:

               If "uv" is a Unicode surrogate code point and "UNICODE_WARN_SURROGATE" is set, the
               function will raise a warning, provided UTF8 warnings are enabled.  If instead
               "UNICODE_DISALLOW_SURROGATE" is set, the function will fail and return NULL.  If
               both flags are set, the function will both warn and return NULL.

               Similarly, the "UNICODE_WARN_NONCHAR" and "UNICODE_DISALLOW_NONCHAR" flags affect
               how the function handles a Unicode non-character.

               And likewise, the "UNICODE_WARN_SUPER" and "UNICODE_DISALLOW_SUPER" flags affect
               the handling of code points that are above the Unicode maximum of 0x10FFFF.
               Languages other than Perl may not be able to accept files that contain these.

               The flag "UNICODE_WARN_ILLEGAL_INTERCHANGE" selects all three of the above WARN
               flags; and "UNICODE_DISALLOW_ILLEGAL_INTERCHANGE" selects all three DISALLOW
               flags.  "UNICODE_DISALLOW_ILLEGAL_INTERCHANGE" restricts the allowed inputs to the
               strict UTF-8 traditionally defined by Unicode.  Similarly,
               "UNICODE_WARN_ILLEGAL_C9_INTERCHANGE" and
               "UNICODE_DISALLOW_ILLEGAL_C9_INTERCHANGE" are shortcuts to select the above-
               Unicode and surrogate flags, but not the non-character ones, as defined in Unicode
               Corrigendum #9 <http://www.unicode.org/versions/corrigendum9.html>.  See
               "Noncharacter code points" in perlunicode.

               Code points above 0x7FFF_FFFF (2**31 - 1) were never specified in any standard, so
               using them is more problematic than other above-Unicode code points.  Perl
               invented an extension to UTF-8 to represent the ones above 2**36-1, so it is
               likely that non-Perl languages will not be able to read files that contain these
               that written by the perl interpreter; nor would Perl understand files written by
               something that uses a different extension.  For these reasons, there is a separate
               set of flags that can warn and/or disallow these extremely high code points, even
               if other above-Unicode ones are accepted.  These are the
               "UNICODE_WARN_ABOVE_31_BIT" and "UNICODE_DISALLOW_ABOVE_31_BIT" flags.  These are
               entirely independent from the deprecation warning for code points above "IV_MAX".
               On 32-bit machines, it will eventually be forbidden to have any code point that
               needs more than 31 bits to represent.  When that happens, effectively the
               "UNICODE_DISALLOW_ABOVE_31_BIT" flag will always be set on 32-bit machines.  (Of
               course "UNICODE_DISALLOW_SUPER" will treat all above-Unicode code points,
               including these, as malformations; and "UNICODE_WARN_SUPER" warns on these.)

               On EBCDIC platforms starting in Perl v5.24, the Perl extension for representing
               extremely high code points kicks in at 0x3FFF_FFFF (2**30 -1), which is lower than
               on ASCII.  Prior to that, code points 2**31 and higher were simply
               unrepresentable, and a different, incompatible method was used to represent code
               points between 2**30 and 2**31 - 1.  The flags "UNICODE_WARN_ABOVE_31_BIT" and
               "UNICODE_DISALLOW_ABOVE_31_BIT" have the same function as on ASCII platforms,
               warning and disallowing 2**31 and higher.

                       U8*     uvchr_to_utf8_flags(U8 *d, UV uv, UV flags)

       uvoffuni_to_utf8_flags
               THIS FUNCTION SHOULD BE USED IN ONLY VERY SPECIALIZED CIRCUMSTANCES.  Instead,
               Almost all code should use "uvchr_to_utf8" or "uvchr_to_utf8_flags".

               This function is like them, but the input is a strict Unicode (as opposed to
               native) code point.  Only in very rare circumstances should code not be using the
               native code point.

               For details, see the description for "uvchr_to_utf8_flags".

                       U8*     uvoffuni_to_utf8_flags(U8 *d, UV uv,
                                                      const UV flags)

       uvuni_to_utf8_flags
               Instead you almost certainly want to use "uvchr_to_utf8" or "uvchr_to_utf8_flags".

               This function is a deprecated synonym for "uvoffuni_to_utf8_flags", which itself,
               while not deprecated, should be used only in isolated circumstances.  These
               functions were useful for code that wanted to handle both EBCDIC and ASCII
               platforms with Unicode properties, but starting in Perl v5.20, the distinctions
               between the platforms have mostly been made invisible to most code, so this
               function is quite unlikely to be what you want.

                       U8*     uvuni_to_utf8_flags(U8 *d, UV uv, UV flags)

       valid_utf8_to_uvchr
               Like "utf8_to_uvchr_buf", but should only be called when it is known that the next
               character in the input UTF-8 string "s" is well-formed (e.g., it passes
               "isUTF8_CHAR".  Surrogates, non-character code points, and non-Unicode code points
               are allowed.

                       UV      valid_utf8_to_uvchr(const U8 *s, STRLEN *retlen)

Variables created by "xsubpp" and "xsubpp" internal functions

       newXSproto
               Used by "xsubpp" to hook up XSUBs as Perl subs.  Adds Perl prototypes to the subs.

       XS_APIVERSION_BOOTCHECK
               Macro to verify that the perl api version an XS module has been compiled against
               matches the api version of the perl interpreter it's being loaded into.

                               XS_APIVERSION_BOOTCHECK;

       XS_VERSION
               The version identifier for an XS module.  This is usually handled automatically by
               "ExtUtils::MakeMaker".  See "XS_VERSION_BOOTCHECK".

       XS_VERSION_BOOTCHECK
               Macro to verify that a PM module's $VERSION variable matches the XS module's
               "XS_VERSION" variable.  This is usually handled automatically by "xsubpp".  See
               "The VERSIONCHECK: Keyword" in perlxs.

                               XS_VERSION_BOOTCHECK;

Warning and Dieing

       ckWARN  Returns a boolean as to whether or not warnings are enabled for the warning
               category "w".  If the category is by default enabled even if not within the scope
               of "use warnings", instead use the "ckWARN_d" macro.

                       bool    ckWARN(U32 w)

       ckWARN2 Like "ckWARN", but takes two warnings categories as input, and returns TRUE if
               either is enabled.  If either category is by default enabled even if not within
               the scope of "use warnings", instead use the "ckWARN2_d" macro.  The categories
               must be completely independent, one may not be subclassed from the other.

                       bool    ckWARN2(U32 w1, U32 w2)

       ckWARN3 Like "ckWARN2", but takes three warnings categories as input, and returns TRUE if
               any is enabled.  If any of the categories is by default enabled even if not within
               the scope of "use warnings", instead use the "ckWARN3_d" macro.  The categories
               must be completely independent, one may not be subclassed from any other.

                       bool    ckWARN3(U32 w1, U32 w2, U32 w3)

       ckWARN4 Like "ckWARN3", but takes four warnings categories as input, and returns TRUE if
               any is enabled.  If any of the categories is by default enabled even if not within
               the scope of "use warnings", instead use the "ckWARN4_d" macro.  The categories
               must be completely independent, one may not be subclassed from any other.

                       bool    ckWARN4(U32 w1, U32 w2, U32 w3, U32 w4)

       ckWARN_d
               Like "ckWARN", but for use if and only if the warning category is by default
               enabled even if not within the scope of "use warnings".

                       bool    ckWARN_d(U32 w)

       ckWARN2_d
               Like "ckWARN2", but for use if and only if either warning category is by default
               enabled even if not within the scope of "use warnings".

                       bool    ckWARN2_d(U32 w1, U32 w2)

       ckWARN3_d
               Like "ckWARN3", but for use if and only if any of the warning categories is by
               default enabled even if not within the scope of "use warnings".

                       bool    ckWARN3_d(U32 w1, U32 w2, U32 w3)

       ckWARN4_d
               Like "ckWARN4", but for use if and only if any of the warning categories is by
               default enabled even if not within the scope of "use warnings".

                       bool    ckWARN4_d(U32 w1, U32 w2, U32 w3, U32 w4)

       croak   This is an XS interface to Perl's "die" function.

               Take a sprintf-style format pattern and argument list.  These are used to generate
               a string message.  If the message does not end with a newline, then it will be
               extended with some indication of the current location in the code, as described
               for "mess_sv".

               The error message will be used as an exception, by default returning control to
               the nearest enclosing "eval", but subject to modification by a $SIG{__DIE__}
               handler.  In any case, the "croak" function never returns normally.

               For historical reasons, if "pat" is null then the contents of "ERRSV" ($@) will be
               used as an error message or object instead of building an error message from
               arguments.  If you want to throw a non-string object, or build an error message in
               an SV yourself, it is preferable to use the "croak_sv" function, which does not
               involve clobbering "ERRSV".

                       void    croak(const char *pat, ...)

       croak_no_modify
               Exactly equivalent to "Perl_croak(aTHX_ "%s", PL_no_modify)", but generates terser
               object code than using "Perl_croak".  Less code used on exception code paths
               reduces CPU cache pressure.

                       void    croak_no_modify()

       croak_sv
               This is an XS interface to Perl's "die" function.

               "baseex" is the error message or object.  If it is a reference, it will be used
               as-is.  Otherwise it is used as a string, and if it does not end with a newline
               then it will be extended with some indication of the current location in the code,
               as described for "mess_sv".

               The error message or object will be used as an exception, by default returning
               control to the nearest enclosing "eval", but subject to modification by a
               $SIG{__DIE__} handler.  In any case, the "croak_sv" function never returns
               normally.

               To die with a simple string message, the "croak" function may be more convenient.

                       void    croak_sv(SV *baseex)

       die     Behaves the same as "croak", except for the return type.  It should be used only
               where the "OP *" return type is required.  The function never actually returns.

                       OP *    die(const char *pat, ...)

       die_sv  Behaves the same as "croak_sv", except for the return type.  It should be used
               only where the "OP *" return type is required.  The function never actually
               returns.

                       OP *    die_sv(SV *baseex)

       vcroak  This is an XS interface to Perl's "die" function.

               "pat" and "args" are a sprintf-style format pattern and encapsulated argument
               list.  These are used to generate a string message.  If the message does not end
               with a newline, then it will be extended with some indication of the current
               location in the code, as described for "mess_sv".

               The error message will be used as an exception, by default returning control to
               the nearest enclosing "eval", but subject to modification by a $SIG{__DIE__}
               handler.  In any case, the "croak" function never returns normally.

               For historical reasons, if "pat" is null then the contents of "ERRSV" ($@) will be
               used as an error message or object instead of building an error message from
               arguments.  If you want to throw a non-string object, or build an error message in
               an SV yourself, it is preferable to use the "croak_sv" function, which does not
               involve clobbering "ERRSV".

                       void    vcroak(const char *pat, va_list *args)

       vwarn   This is an XS interface to Perl's "warn" function.

               "pat" and "args" are a sprintf-style format pattern and encapsulated argument
               list.  These are used to generate a string message.  If the message does not end
               with a newline, then it will be extended with some indication of the current
               location in the code, as described for "mess_sv".

               The error message or object will by default be written to standard error, but this
               is subject to modification by a $SIG{__WARN__} handler.

               Unlike with "vcroak", "pat" is not permitted to be null.

                       void    vwarn(const char *pat, va_list *args)

       warn    This is an XS interface to Perl's "warn" function.

               Take a sprintf-style format pattern and argument list.  These are used to generate
               a string message.  If the message does not end with a newline, then it will be
               extended with some indication of the current location in the code, as described
               for "mess_sv".

               The error message or object will by default be written to standard error, but this
               is subject to modification by a $SIG{__WARN__} handler.

               Unlike with "croak", "pat" is not permitted to be null.

                       void    warn(const char *pat, ...)

       warn_sv This is an XS interface to Perl's "warn" function.

               "baseex" is the error message or object.  If it is a reference, it will be used
               as-is.  Otherwise it is used as a string, and if it does not end with a newline
               then it will be extended with some indication of the current location in the code,
               as described for "mess_sv".

               The error message or object will by default be written to standard error, but this
               is subject to modification by a $SIG{__WARN__} handler.

               To warn with a simple string message, the "warn" function may be more convenient.

                       void    warn_sv(SV *baseex)

Undocumented functions

       The following functions have been flagged as part of the public API, but are currently
       undocumented.  Use them at your own risk, as the interfaces are subject to change.
       Functions that are not listed in this document are not intended for public use, and should
       NOT be used under any circumstances.

       If you feel you need to use one of these functions, first send email to
       perl5-porters@perl.org <mailto:perl5-porters@perl.org>.  It may be that there is a good
       reason for the function not being documented, and it should be removed from this list; or
       it may just be that no one has gotten around to documenting it.  In the latter case, you
       will be asked to submit a patch to document the function.  Once your patch is accepted, it
       will indicate that the interface is stable (unless it is explicitly marked otherwise) and
       usable by you.

       GetVars
       Gv_AMupdate
       PerlIO_clearerr
       PerlIO_close
       PerlIO_context_layers
       PerlIO_eof
       PerlIO_error
       PerlIO_fileno
       PerlIO_fill
       PerlIO_flush
       PerlIO_get_base
       PerlIO_get_bufsiz
       PerlIO_get_cnt
       PerlIO_get_ptr
       PerlIO_read
       PerlIO_seek
       PerlIO_set_cnt
       PerlIO_set_ptrcnt
       PerlIO_setlinebuf
       PerlIO_stderr
       PerlIO_stdin
       PerlIO_stdout
       PerlIO_tell
       PerlIO_unread
       PerlIO_write
       amagic_call
       amagic_deref_call
       any_dup
       atfork_lock
       atfork_unlock
       av_arylen_p
       av_iter_p
       block_gimme
       call_atexit
       call_list
       calloc
       cast_i32
       cast_iv
       cast_ulong
       cast_uv
       ck_warner
       ck_warner_d
       ckwarn
       ckwarn_d
       clear_defarray
       clone_params_del
       clone_params_new
       croak_memory_wrap
       croak_nocontext
       csighandler
       cx_dump
       cx_dup
       cxinc
       deb
       deb_nocontext
       debop
       debprofdump
       debstack
       debstackptrs
       delimcpy
       despatch_signals
       die_nocontext
       dirp_dup
       do_aspawn
       do_binmode
       do_close
       do_gv_dump
       do_gvgv_dump
       do_hv_dump
       do_join
       do_magic_dump
       do_op_dump
       do_open
       do_open9
       do_openn
       do_pmop_dump
       do_spawn
       do_spawn_nowait
       do_sprintf
       do_sv_dump
       doing_taint
       doref
       dounwind
       dowantarray
       dump_eval
       dump_form
       dump_indent
       dump_mstats
       dump_sub
       dump_vindent
       filter_add
       filter_del
       filter_read
       foldEQ_latin1
       form_nocontext
       fp_dup
       fprintf_nocontext
       free_global_struct
       free_tmps
       get_context
       get_mstats
       get_op_descs
       get_op_names
       get_ppaddr
       get_vtbl
       gp_dup
       gp_free
       gp_ref
       gv_AVadd
       gv_HVadd
       gv_IOadd
       gv_SVadd
       gv_add_by_type
       gv_autoload4
       gv_autoload_pv
       gv_autoload_pvn
       gv_autoload_sv
       gv_check
       gv_dump
       gv_efullname
       gv_efullname3
       gv_efullname4
       gv_fetchfile
       gv_fetchfile_flags
       gv_fetchpv
       gv_fetchpvn_flags
       gv_fetchsv
       gv_fullname
       gv_fullname3
       gv_fullname4
       gv_handler
       gv_name_set
       he_dup
       hek_dup
       hv_common
       hv_common_key_len
       hv_delayfree_ent
       hv_eiter_p
       hv_eiter_set
       hv_free_ent
       hv_ksplit
       hv_name_set
       hv_placeholders_get
       hv_placeholders_set
       hv_rand_set
       hv_riter_p
       hv_riter_set
       ibcmp_utf8
       init_global_struct
       init_stacks
       init_tm
       instr
       is_lvalue_sub
       leave_scope
       load_module_nocontext
       magic_dump
       malloc
       markstack_grow
       mess_nocontext
       mfree
       mg_dup
       mg_size
       mini_mktime
       moreswitches
       mro_get_from_name
       mro_get_private_data
       mro_set_mro
       mro_set_private_data
       my_atof
       my_atof2
       my_bcopy
       my_bzero
       my_chsize
       my_cxt_index
       my_cxt_init
       my_dirfd
       my_exit
       my_failure_exit
       my_fflush_all
       my_fork
       my_lstat
       my_memcmp
       my_memset
       my_pclose
       my_popen
       my_popen_list
       my_setenv
       my_socketpair
       my_stat
       my_strftime
       newANONATTRSUB
       newANONHASH
       newANONLIST
       newANONSUB
       newATTRSUB
       newAVREF
       newCVREF
       newFORM
       newGVREF
       newGVgen
       newGVgen_flags
       newHVREF
       newHVhv
       newIO
       newMYSUB
       newPROG
       newRV
       newSUB
       newSVREF
       newSVpvf_nocontext
       new_stackinfo
       op_refcnt_lock
       op_refcnt_unlock
       parser_dup
       perl_alloc_using
       perl_clone_using
       pmop_dump
       pop_scope
       pregcomp
       pregexec
       pregfree
       pregfree2
       printf_nocontext
       ptr_table_fetch
       ptr_table_free
       ptr_table_new
       ptr_table_split
       ptr_table_store
       push_scope
       re_compile
       re_dup_guts
       re_intuit_start
       re_intuit_string
       realloc
       reentrant_free
       reentrant_init
       reentrant_retry
       reentrant_size
       ref
       reg_named_buff_all
       reg_named_buff_exists
       reg_named_buff_fetch
       reg_named_buff_firstkey
       reg_named_buff_nextkey
       reg_named_buff_scalar
       regdump
       regdupe_internal
       regexec_flags
       regfree_internal
       reginitcolors
       regnext
       repeatcpy
       rsignal
       rsignal_state
       runops_debug
       runops_standard
       rvpv_dup
       safesyscalloc
       safesysfree
       safesysmalloc
       safesysrealloc
       save_I16
       save_I32
       save_I8
       save_adelete
       save_aelem
       save_aelem_flags
       save_alloc
       save_aptr
       save_ary
       save_bool
       save_clearsv
       save_delete
       save_destructor
       save_destructor_x
       save_freeop
       save_freepv
       save_freesv
       save_generic_pvref
       save_generic_svref
       save_hash
       save_hdelete
       save_helem
       save_helem_flags
       save_hints
       save_hptr
       save_int
       save_item
       save_iv
       save_list
       save_long
       save_mortalizesv
       save_nogv
       save_op
       save_padsv_and_mortalize
       save_pptr
       save_pushi32ptr
       save_pushptr
       save_pushptrptr
       save_re_context
       save_scalar
       save_set_svflags
       save_shared_pvref
       save_sptr
       save_svref
       save_vptr
       savestack_grow
       savestack_grow_cnt
       scan_num
       scan_vstring
       seed
       set_context
       set_numeric_local
       set_numeric_radix
       set_numeric_standard
       share_hek
       si_dup
       ss_dup
       stack_grow
       start_subparse
       str_to_version
       sv_2iv
       sv_2pv
       sv_2uv
       sv_catpvf_mg_nocontext
       sv_catpvf_nocontext
       sv_dup
       sv_dup_inc
       sv_peek
       sv_pvn_nomg
       sv_setpvf_mg_nocontext
       sv_setpvf_nocontext
       sys_init
       sys_init3
       sys_intern_clear
       sys_intern_dup
       sys_intern_init
       sys_term
       taint_env
       taint_proper
       unlnk
       unsharepvn
       utf16_to_utf8
       utf16_to_utf8_reversed
       uvuni_to_utf8
       vdeb
       vform
       vload_module
       vnewSVpvf
       vwarner
       warn_nocontext
       warner
       warner_nocontext
       whichsig
       whichsig_pv
       whichsig_pvn
       whichsig_sv

AUTHORS

       Until May 1997, this document was maintained by Jeff Okamoto <okamoto@corp.hp.com>.  It is
       now maintained as part of Perl itself.

       With lots of help and suggestions from Dean Roehrich, Malcolm Beattie, Andreas Koenig,
       Paul Hudson, Ilya Zakharevich, Paul Marquess, Neil Bowers, Matthew Green, Tim Bunce,
       Spider Boardman, Ulrich Pfeifer, Stephen McCamant, and Gurusamy Sarathy.

       API Listing originally by Dean Roehrich <roehrich@cray.com>.

       Updated to be autogenerated from comments in the source by Benjamin Stuhl.

SEE ALSO

       perlguts, perlxs, perlxstut, perlintern