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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.  Any functions not listed
       here are 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.

       Note that all Perl API global variables must be referenced with the "PL_" prefix.  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.

       Note that Perl can be compiled and run under EBCDIC (See perlebcdic) or ASCII.  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 more bytes than in UTF-8.

       The listing below is alphabetical, case insensitive.

"Gimme" Values

       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_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.

       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.

Array Manipulation Functions

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

                       int     AvFILL(AV* av)

       av_clear
               Clears an array, making it empty.  Does not free the memory the av uses to store
               its list of scalars.  If any destructors are triggered as a result, the av itself
               may be freed when this function returns.

               Perl equivalent: "@myarray = ();".

                       void    av_clear(AV *av)

       av_create_and_push
               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.

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

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

       av_create_and_unshift_one
               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.

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

                       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.  Perl equivalent: "my $elem = delete($myarray[$idx]);" for the
               non-"G_DISCARD" version and a void-context "delete($myarray[$idx]);" for the
               "G_DISCARD" version.

                       SV*     av_delete(AV *av, I32 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 &PL_sv_undef.

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

                       bool    av_exists(AV *av, I32 key)

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

                       void    av_extend(AV *av, I32 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 $myarray[$idx].

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

       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 an array will be "fill + 1" after av_fill() returns.
               If the array was previously shorter, then the additional elements appended are set
               to "PL_sv_undef".  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, I32 fill)

       av_len  Same as "av_top_index".  Returns the highest index in the array.  Note that the
               return value is +1 what its name implies it returns; and hence differs in meaning
               from what the similarly named "sv_len" returns.

                       I32     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(I32 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 onto the end of the array.  The array will grow automatically to
               accommodate the addition.  This takes ownership of one reference count.

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

                       void    av_push(AV *av, SV *val)

       av_shift
               Shifts an SV off the beginning of the array.  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: "$myarray[$key] = $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, I32 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".)

                       I32     av_top_index(AV *av)

       av_undef
               Undefines the array.  Frees the memory used by the av to store its list of
               scalars.  If any destructors are triggered as a result, the av itself may be
               freed.

                       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.  You must then use
               "av_store" to assign values to these new elements.

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

                       void    av_unshift(AV *av, I32 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  Sort an array. Here is an example:

                   sortsv(AvARRAY(av), av_top_index(av)+1, Perl_sv_cmp_locale);

               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
               Sort an array, with various 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 whose name is in the SV.  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;

       eval_pv Tells Perl to "eval" the given string 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;

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

                               SAVETMPS;

Character case changing

       toLOWER Converts the specified character to lowercase, if possible; otherwise returns the
               input character itself.

                       char    toLOWER(char ch)

       toUPPER Converts the specified character to uppercase, if possible; otherwise returns the
               input character itself.

                       char    toUPPER(char ch)

Character classes

       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".

       Variant "isFOO_L1" imposes the Latin-1 (or EBCDIC equivlalent) 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 represent different
       characters in each).

       Variant "isFOO_uni" 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_uni(0x100)" returns TRUE, since 0x100 is
       LATIN CAPITAL LETTER A WITH MACRON in Unicode, and is a word character.

       Variant "isFOO_utf8" is like "isFOO_uni", but the input is a pointer to a (known to be
       well-formed) UTF-8 encoded string ("U8*" or "char*").  The classification of just the
       first (possibly multi-byte) character in the string is tested.

       Variant "isFOO_LC" is like the "isFOO_A" and "isFOO_L1" variants, but uses the C library
       function that gives the named classification instead of hard-coded rules.  For example,
       "isDIGIT_LC()" returns the result of calling "isdigit()".  This means that the result is
       based on the current locale, which is what "LC" in the name stands for.  FALSE is always
       returned if the input won't fit into an octet.

       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" is like "isFOO_LC_uvchr", but the input is a pointer to a (known
       to be well-formed) UTF-8 encoded string ("U8*" or "char*").  The classification of just
       the first (possibly multi-byte) character in the string is tested.

       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_uni", "isALPHA_utf8",
               "isALPHA_LC", "isALPHA_LC_uvchr", and "isALPHA_LC_utf8".

                       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_uni", "isALPHANUMERIC_utf8",
               "isALPHANUMERIC_LC", "isALPHANUMERIC_LC_uvchr", and "isALPHANUMERIC_LC_utf8".

                       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_uni", "isASCII_utf8", "isASCII_LC", "isASCII_LC_uvchr", and
               "isASCII_LC_utf8".  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.

                       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_uni",
               "isBLANK_utf8", "isBLANK_LC", "isBLANK_LC_uvchr", and "isBLANK_LC_utf8".  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_uni", "isCNTRL_utf8",
               "isCNTRL_LC", "isCNTRL_LC_uvchr", and "isCNTRL_LC_utf8" 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_uni", "isDIGIT_utf8", "isDIGIT_LC", "isDIGIT_LC_uvchr", and
               "isDIGIT_LC_utf8".

                       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_uni", "isGRAPH_utf8",
               "isGRAPH_LC", "isGRAPH_LC_uvchr", and "isGRAPH_LC_utf8".

                       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_uni", "isIDCONT_utf8", "isIDCONT_LC", "isIDCONT_LC_uvchr", and
               "isIDCONT_LC_utf8".

                       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_uni", "isIDFIRST_utf8", "isIDFIRST_LC", "isIDFIRST_LC_uvchr", and
               "isIDFIRST_LC_utf8".

                       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_uni", "isLOWER_utf8",
               "isLOWER_LC", "isLOWER_LC_uvchr", and "isLOWER_LC_utf8".

                       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_uni", "isPRINT_utf8",
               "isPRINT_LC", "isPRINT_LC_uvchr", and "isPRINT_LC_utf8".

                       bool    isPRINT(char ch)

       isPSXSPC
               (short for Posix Space) Starting in 5.18, this is identical (experimentally) in
               all its forms to the corresponding "isSPACE()" macros.  ("Experimentally" means
               that this change may be backed out in 5.20 or 5.22 if field experience indicates
               that it was unwise.)  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_uni",
               "isPSXSPC_utf8", "isPSXSPC_LC", "isPSXSPC_LC_uvchr", and "isPSXSPC_LC_utf8".

                       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_uni", "isPUNCT_utf8",
               "isPUNCT_LC", "isPUNCT_LC_uvchr", and "isPUNCT_LC_utf8".

                       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 (experimentally), this also matches what "m/[[:space:]]/"
               does.  ("Experimentally" means that this change may be backed out in 5.20 or 5.22
               if field experience indicates that it was unwise.)  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_uni",
               "isSPACE_utf8", "isSPACE_LC", "isSPACE_LC_uvchr", and "isSPACE_LC_utf8".

                       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_uni", "isUPPER_utf8",
               "isUPPER_LC", "isUPPER_LC_uvchr", and "isUPPER_LC_utf8".

                       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_uni", "isWORDCHAR_utf8", "isWORDCHAR_LC", "isWORDCHAR_LC_uvchr", and
               "isWORDCHAR_LC_utf8".

                       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_uni", "isXDIGIT_utf8", "isXDIGIT_LC",
               "isXDIGIT_LC_uvchr", and "isXDIGIT_LC_utf8".

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

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

                       void    BhkDISABLE(BHK *hk, which)

       BhkENABLE
               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.

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

                       void    BhkENABLE(BHK *hk, which)

       BhkENTRY_set
               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.

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

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

       blockhook_register
               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 is experimental and may change or be removed without notice.

               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
               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.

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

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

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

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

                       COPHH * cophh_copy(COPHH *cophh)

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

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

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

       cophh_delete_pvn
               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.

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

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

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

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

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

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

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

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

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

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

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

       cophh_fetch_pvn
               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.

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

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

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

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

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

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

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

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

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

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

                       void    cophh_free(COPHH *cophh)

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

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

                       COPHH * cophh_new_empty()

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

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

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

       cophh_store_pvn
               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.

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

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

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

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

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

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

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

                       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 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 function should be considered
               internal to OP_NAME and the other access macros: use them instead.

               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.

                               XopENTRY(XOP *xop, 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.

                       void    XopENTRY_set(XOP *xop, which, value)

       XopFLAGS
               Return the XOP's flags.

                       U32     XopFLAGS(XOP *xop)

CV Manipulation Functions

       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)

       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)

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_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
               Find and return the variable that is named $_ in the lexical scope of the
               currently-executing function.  This may be a lexical $_, or will otherwise be the
               global one.

                       SV *    find_rundefsv()

       find_rundefsvoffset
               Find the position of the lexical $_ in the pad of the currently-executing
               function.  Returns the offset in the current pad, or "NOT_IN_PAD" if there is no
               lexical $_ in scope (in which case the global one should be used instead).
               "find_rundefsv" is likely to be more convenient.

               NOTE: the perl_ form of this function is deprecated.

                       PADOFFSET find_rundefsvoffset()

       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".  flags can be any of PERL_LOADMOD_DENY, PERL_LOADMOD_NOIMPORT, or
               PERL_LOADMOD_IMPORT_OPS (or 0 for no flags). ver, if specified and not NULL,
               provides version semantics similar to "use Foo::Bar VERSION".  The optional
               trailing SV* arguments can be used to specify arguments to the module's import()
               method, similar to "use Foo::Bar VERSION LIST".  They must be terminated with a
               final NULL pointer.  Note that this list can only be omitted when the
               PERL_LOADMOD_NOIMPORT flag has been used.  Otherwise at least a single NULL
               pointer to designate the default import list is required.

               The reference count for each specified "SV*" parameter is decremented.

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

       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
               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

               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.

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

                       PADOFFSET pad_alloc(I32 optype, U32 tmptype)

       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)

       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)

       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
               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

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

                       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)

Functions in file dump.c

       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.

               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 Unicode, if
               PERL_PV_ESCAPE_UNI_DETECT is set then the input string is scanned using
               "is_utf8_string()" to determine if it is Unicode.

               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 chars above 127
               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)

Functions in file mathoms.c

       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)

       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)

       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)

Functions in file op.c

       alloccopstash
               Available only under threaded builds, this function allocates an entry in
               "PL_stashpad" for the stash passed to it.

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

                       PADOFFSET alloccopstash(HV *hv)

       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)

Functions in file perl.h

       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()

Functions in file pp_ctl.c

       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
                                            )

       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. (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)

Functions in file pp_pack.c

       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)

Functions in file pp_sys.c

       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)

Functions in file utf8.h

       ibcmp_utf8
               This is a synonym for (! foldEQ_utf8())

                       I32     ibcmp_utf8(const char *s1, char **pe1, UV l1,
                                          bool u1, const char *s2, char **pe2,
                                          UV l2, bool u2)

Functions in file util.h

       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)

Global Variables

       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
               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".

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

GV Functions

       GvAV    Return the AV from the GV.

                       AV*     GvAV(GV* gv)

       GvCV    Return the CV from the GV.

                       CV*     GvCV(GV* gv)

       GvHV    Return the HV from the GV.

                       HV*     GvHV(GV* gv)

       GvSV    Return the SV from the GV.

                       SV*     GvSV(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)

       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 via a side effect to do
               this.

               These functions have the same side-effects and as "gv_fetchmeth" with "level==0".
               "name" should be writable if contains ':' or ' ''. The warning against passing the
               GV returned by "gv_fetchmeth" to "call_sv" apply 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)

       gv_init The old form of gv_init_pvn().  It does not work with UTF8 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 UTF8 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.

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

       gv_stashpvs
               Like "gv_stashpvn", but takes a 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".

                       HV*     gv_stashsv(SV* sv, I32 flags)

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

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

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

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

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

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

                       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".

                       char*   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)

       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 UTF8 encoding.

                       unsigned char HvENAMEUTF8(HV *stash)

       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 UTF8 encoding.

                       unsigned char HvNAMEUTF8(HV *stash)

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

                       void    hv_assert(HV *hv)

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

               If any destructors are triggered as a result, the hv itself may be freed.

                       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)

       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 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".

               Previously this value was stored in the HV structure, rather than being calculated
               on demand.

                       STRLEN  hv_fill(HV const *const hv)

       hv_iterinit
               Prepares a starting point to traverse a hash table.  Returns the number of keys in
               the hash (i.e. the same as "HvUSEDKEYS(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
               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.

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

                       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)

       hv_scalar
               Evaluates the hash in scalar context and returns the result. Handles magic when
               the hash is tied.

                       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 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.

               If any destructors are triggered as a result, the hv itself may be freed.

               See also "hv_clear".

                       void    hv_undef(HV *hv)

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

                       HV*     newHV()

Hook manipulation

       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.

               "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

       lex_bufutf8
               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.

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

                       bool    lex_bufutf8()

       lex_discard_to
               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.

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

                       void    lex_discard_to(char *ptr)

       lex_grow_linestr
               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.

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

                       char *  lex_grow_linestr(STRLEN len)

       lex_next_chunk
               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 includes
               "LEX_KEEP_PREVIOUS", 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.

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

                       bool    lex_next_chunk(U32 flags)

       lex_peek_unichar
               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 includes "LEX_KEEP_PREVIOUS" 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.

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

                       I32     lex_peek_unichar(U32 flags)

       lex_read_space
               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
               includes "LEX_KEEP_PREVIOUS" then the current chunk will not be discarded.

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

                       void    lex_read_space(U32 flags)

       lex_read_to
               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".

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

                       void    lex_read_to(char *ptr)

       lex_read_unichar
               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 includes "LEX_KEEP_PREVIOUS" 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.

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

                       I32     lex_read_unichar(U32 flags)

       lex_start
               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.

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

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

       lex_stuff_pv
               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.

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

                       void    lex_stuff_pv(const char *pv, U32 flags)

       lex_stuff_pvn
               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.

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

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

       lex_stuff_pvs
               Like "lex_stuff_pvn", but takes a literal string instead of a string/length pair.

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

                       void    lex_stuff_pvs(const char *pv, U32 flags)

       lex_stuff_sv
               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.

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

                       void    lex_stuff_sv(SV *sv, U32 flags)

       lex_unstuff
               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".

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

                       void    lex_unstuff(char *ptr)

       parse_arithexpr
               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 includes
               "PARSE_OPTIONAL" 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.

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

                       OP *    parse_arithexpr(U32 flags)

       parse_barestmt
               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.

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

                       OP *    parse_barestmt(U32 flags)

       parse_block
               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.

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

                       OP *    parse_block(U32 flags)

       parse_fullexpr
               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
               includes "PARSE_OPTIONAL" 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.

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

                       OP *    parse_fullexpr(U32 flags)

       parse_fullstmt
               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.

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

                       OP *    parse_fullstmt(U32 flags)

       parse_label
               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 includes "PARSE_OPTIONAL" 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.

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

                       SV *    parse_label(U32 flags)

       parse_listexpr
               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 includes
               "PARSE_OPTIONAL" 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.

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

                       OP *    parse_listexpr(U32 flags)

       parse_stmtseq
               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.

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

                       OP *    parse_stmtseq(U32 flags)

       parse_termexpr
               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 includes "PARSE_OPTIONAL"
               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.

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

                       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
               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.

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

       PL_parser->bufptr
               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".

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

       PL_parser->linestart
               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.

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

       PL_parser->linestr
               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.

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

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
               This function is deprecated.

               It reports on the SV's length in bytes, calling length magic if available, but
               does not set the UTF8 flag on the 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 the 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* dsb, 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.

                       void    SvSetSV(SV* dsb, 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.

               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".

                       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".

                       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.

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

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

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

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

                       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()". The
               memory allocated for the new string can be freed with the "Safefree()" function.

                       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.

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

       savepvs Like "savepvn", but takes a 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()"

                       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

       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".  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 the sv with current working directory

                       int     getcwd_sv(SV* sv)

       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_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)

       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)

       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*)

       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)

       strEQ   Test two strings to see if they are equal.  Returns true or false.

                       bool    strEQ(char* s1, char* s2)

       strGE   Test two 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 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 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 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 strings to see if they are different.  Returns true or false.

                       bool    strNE(char* s1, char* s2)

       strnEQ  Test two 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 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)

       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)

       vmess   "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".

               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)

       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):

                       SV*     vverify(SV *vs)

MRO Functions

       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 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_number
               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 an in UV, it is returned in the *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.

                       int     grok_number(const char *pv, STRLEN len,
                                           UV *valuep)

       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)

       Perl_signbit
               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.  As a first pass, this gets everything right except -0.0.  Alas,
               catching -0.0 is the main use for this function, so this is not too helpful yet.
               Still, at least we have the scaffolding in place to support other systems, should
               that prove useful.

               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().

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

                       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)

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)

       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 $_ (either lexical or global).  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 is the pad offset
               of the scalar lexical variable that will be affected.  If it is 0, the global $_
               will be used.

                       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.

                       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)

       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)

       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

       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
               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 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 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.

               The current setting for a particular CV can be retrieved by "cv_get_call_checker".

                       void    cv_set_call_checker(CV *cv,
                                                   Perl_call_checker ckfun,
                                                   SV *ckobj)

       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.  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_DESC Return a short description of the provided OP.

                       const char * OP_DESC(OP *o)

       op_linklist
               This function is the implementation of the "LINKLIST" macro. It should not be
               called directly.

                       OP*     op_linklist(OP *o)

       op_lvalue
               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.

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

                       OP *    op_lvalue(OP *o, I32 type)

       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_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
               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.

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

                       OP *    op_scope(OP *o)

       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)

Pad Data Structures

       CvPADLIST
               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 don't have CvPADLIST set - dXSTARG fetches values from PL_curpad, but that
               is really the callers pad (a slot of which is allocated by every entersub).

               The PADLIST has a C array where pads are stored.

               The 0th entry of the PADLIST is a PADNAMELIST (which is actually just an AV, but
               that may change) which represents the "names" or rather the "static type
               information" for lexicals.  The individual elements of a PADNAMELIST are PADNAMEs
               (just SVs; but, again, that may change).  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
               that are SVs_PADTMP (targets/GVs/constants) end up having &PL_sv_undef "names"
               (see pad_alloc()).

               Only my/our variable (SvPADMY/PADNAME_isOUR) 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 SVs in the names AV have their PV being the name of the variable.
               xlow+1..xhigh inclusive in the NV union is a range of cop_seq numbers for which
               the name is valid (accessed through the macros COP_SEQ_RANGE_LOW and _HIGH).
               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) }

               For typed lexicals name SV is SVt_PVMG and SvSTASH points at the type.  For "our"
               lexicals, the type is also SVt_PVMG, with the SvOURSTASH slot pointing at the
               stash of the associated global (so that duplicate "our" declarations in the same
               package can be detected).  SvUVX is sometimes hijacked to store the generation
               number during compilation.

               If PADNAME_OUTER (SvFAKE) is set on the name SV, then that slot in the frame AV is
               a REFCNT'ed reference to a lexical from "outside". In this case, the name SV does
               not use xlow and xhigh to store a cop_seq range, since it is in scope throughout.
               Instead xhigh 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, xlow 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.  (PADNAME_OUTER and name of '&' is not a meaningful combination
               currently but could become so if "my sub foo {}" is implemented.)

               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'.

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

                       PADLIST * CvPADLIST(CV *cv)

       PadARRAY
               The C array of pad entries.

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

                       SV **   PadARRAY(PAD pad)

       PadlistARRAY
               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.

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

                       PAD **  PadlistARRAY(PADLIST padlist)

       PadlistMAX
               The index of the last pad in the padlist.

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

                       SSize_t PadlistMAX(PADLIST padlist)

       PadlistNAMES
               The names associated with pad entries.

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

                       PADNAMELIST * PadlistNAMES(PADLIST padlist)

       PadlistNAMESARRAY
               The C array of pad names.

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

                       PADNAME ** PadlistNAMESARRAY(PADLIST padlist)

       PadlistNAMESMAX
               The index of the last pad name.

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

                       SSize_t PadlistNAMESMAX(PADLIST padlist)

       PadlistREFCNT
               The reference count of the padlist.  Currently this is always 1.

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

                       U32     PadlistREFCNT(PADLIST padlist)

       PadMAX  The index of the last pad entry.

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

                       SSize_t PadMAX(PAD pad)

       PadnameLEN
               The length of the name.

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

                       STRLEN  PadnameLEN(PADNAME pn)

       PadnamelistARRAY
               The C array of pad names.

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

                       PADNAME ** PadnamelistARRAY(PADNAMELIST pnl)

       PadnamelistMAX
               The index of the last pad name.

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

                       SSize_t PadnamelistMAX(PADNAMELIST pnl)

       PadnamePV
               The name stored in the pad name struct.  This returns NULL for a target or GV
               slot.

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

                       char *  PadnamePV(PADNAME pn)

       PadnameSV
               Returns the pad name as an SV.  This is currently just "pn".  It will begin
               returning a new mortal SV if pad names ever stop being SVs.

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

                       SV *    PadnameSV(PADNAME pn)

       PadnameUTF8
               Whether PadnamePV is in UTF8.

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

                       bool    PadnameUTF8(PADNAME pn)

       pad_add_name_pvs
               Exactly like "pad_add_name_pvn", but takes a literal string instead of a
               string/length pair.

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

       pad_findmy_pvs
               Exactly like "pad_findmy_pvn", but takes a literal string instead of a
               string/length pair.

                       PADOFFSET pad_findmy_pvs(const char *name, U32 flags)

       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
               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.

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

       PL_comppad_name
               During compilation, this points to the array containing the names part of the pad
               for the currently-compiling code.

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

       PL_curpad
               Points directly to the body of the "PL_comppad" array.  (I.e., this is
               "PAD_ARRAY(PL_comppad)".)

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

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)

Simple Exception Handling 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.

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, int 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

       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 Flags

       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_BIND (unused)
                   SVt_IV
                   SVt_NV
                   SVt_RV
                   SVt_PV
                   SVt_PVIV
                   SVt_PVNV
                   SVt_PVMG
                   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_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.

       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".

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
               Creates a new SV containing the pad name.  This is currently identical to
               "newSVsv", but pad names may cease being SVs at some point, so "newSVpadname" is
               preferable.

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

                       SV*     newSVpadname(PADNAME *pn)

       newSVpvn_utf8
               Creates a new SV and copies a string 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)

       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)

       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 null (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.

                       char *  SvGROW(SV* sv, STRLEN len)

       SvIOK   Returns a U32 value indicating whether the SV contains an integer.

                       U32     SvIOK(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_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)

       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 boolean 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).

                       bool    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 an integer and returns it.  See "SvIVx" for a version
               which guarantees to evaluate sv only once.

                       IV      SvIV(SV* sv)

       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 an integer and returns it.  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)

       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)

       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 actual length of the string which is in the SV.  See "SvIV_set".

                       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)

       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)

       SvNIOK_off
               Unsets the NV/IV status of an SV.

                       void    SvNIOK_off(SV* sv)

       SvNOK   Returns a U32 value indicating whether the SV contains a double.

                       U32     SvNOK(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)

       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)

       SvNV    Coerce the given SV to a double and return it.  See "SvNVx" for a version which
               guarantees to evaluate sv only once.

                       NV      SvNV(SV* sv)

       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 a double and returns it.  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)

       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)

       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)

       SvPOKp  Returns a U32 value indicating whether the SV contains a character string.  Checks
               the private setting.  Use "SvPOK" instead.

                       U32     SvPOKp(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)

       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.  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)

       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)

       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)

       SvPVutf8
               Like "SvPV", but converts sv to utf8 first if necessary.

                       char*   SvPVutf8(SV* sv, STRLEN len)

       SvPVutf8x
               Like "SvPV", but converts sv to utf8 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 utf8 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 utf8 first if necessary.

                       char*   SvPVutf8_force(SV* sv, STRLEN len)

       SvPVutf8_nolen
               Like "SvPV_nolen", but converts sv to utf8 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)

       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
               Set the value of the PV pointer in sv to val.  See also "SvIV_set".

               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.

                       void    SvPV_set(SV* sv, char* val)

       SvREFCNT
               Returns the value of the object's reference count.

                       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)

       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)

       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.

                       U32     SvUTF8(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 an unsigned integer and returns it.  See "SvUVx" for a
               version which guarantees to evaluate sv only once.

                       UV      SvUV(SV* sv)

       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 an unsigned integer and returns it.  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)

       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)

       SvVOK   Returns a boolean indicating whether the SV contains a v-string.

                       bool    SvVOK(SV* sv)

       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)

       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)

       sv_report_used
               Dump the contents of all SVs not yet freed (debugging aid).

                       void    sv_report_used()

       sv_setsv_nomg
               Like "sv_setsv" but doesn't process magic.

                       void    sv_setsv_nomg(SV* dsv, SV* ssv)

       sv_utf8_upgrade_nomg
               Like sv_utf8_upgrade, but doesn't do magic on "sv".

                       STRLEN  sv_utf8_upgrade_nomg(NN SV *sv)

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 sv)

       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 the
               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 into it.  The reference count for the SV is
               set to 1.  If "len" is zero, Perl will compute the length using strlen().  For
               efficiency, consider using "newSVpvn" instead.

                       SV*     newSVpv(const char *const s, const STRLEN len)

       newSVpvf
               Creates a new SV and initializes it with the string formatted like "sprintf".

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

       newSVpvn
               Creates a new SV and copies a buffer 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 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 literal string instead of a string/length pair.

                       SV*     newSVpvs(const char* s)

       newSVpvs_flags
               Like "newSVpvn_flags", but takes a literal string instead of a string/length pair.

                       SV*     newSVpvs_flags(const char* s, U32 flags)

       newSVpvs_share
               Like "newSVpvn_share", but takes a literal string instead of a string/length pair
               and omits the hash parameter.

                       SV*     newSVpvs_share(const char* s)

       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)

       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)

       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)

       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)

       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 *const sv, const 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 includes SV_GMAGIC, 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 includes SV_GMAGIC, 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 includes SV_GMAGIC, 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 includes SV_GMAGIC, 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.

                       int     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 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 "sprintf" and appends the formatted output to an SV.
               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.  The "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.  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 "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 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 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 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 literal string instead of a string/length pair.

                       void    sv_catpvs_nomg(SV* sv, const char* s)

       sv_catpv_flags
               Concatenates the 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" include
               "SV_GMAGIC" bit set, will call "mg_get" on both SVs if appropriate.  If "flags"
               include "SV_SMAGIC", "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 the "ptr" must be a pointer to
               somewhere inside the string buffer.  The "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 include SV_GMAGIC, 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_flags
               Implementation of sv_copypv and sv_copypv_nomg.  Calls get magic iff flags include
               SV_GMAGIC.

                       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 include SV_GMAGIC, 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.

                       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, deallocate
               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_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 *const 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.

                       void    sv_pos_b2u(SV *const sv, I32 *const offsetp)

       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 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 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 "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_reftype
               Returns a string describing what the SV is a reference to.

                       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 null-terminated.  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 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 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 literal string instead of a string/length pair.

                       void    sv_setpvs_mg(SV* sv, const char* s)

       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 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.  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 "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_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.  The "ptr"
               should point to memory that was allocated by "malloc".  It must be the start of a
               mallocked block of memory, and not a pointer to the middle of it.  The string
               length, "len", must be supplied.  By default this function will realloc (i.e.
               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
               If the PV of the SV is an octet sequence in 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.

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

                       bool    sv_utf8_decode(SV *const sv)

       sv_utf8_downgrade
               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.

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

                       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.  Returns the number of bytes in
               the converted string "sv_utf8_upgrade" and "sv_utf8_upgrade_nomg" are implemented
               in terms of this function.

               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_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 "vsprintf" 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).
               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 include "SV_GMAGIC", 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)

Unicode Support

       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 the 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
               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 utf8 (i.e., US-ASCII on non-EBCDIC machines).

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

                       U8*     bytes_from_utf8(const U8 *s, STRLEN *len,
                                               bool *is_utf8)

       bytes_to_utf8
               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"().

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

                       U8*     bytes_to_utf8(const U8 *s, STRLEN *len)

       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
               Returns true if the first "len" bytes of the string "s" are the same whether or
               not the string is encoded in UTF-8 (or UTF-EBCDIC on EBCDIC machines).  That is,
               if they are invariant.  On ASCII-ish machines, only ASCII characters fit this
               definition, hence the function's name.

               If "len" is 0, it will be calculated using strlen(s).

               See also "is_utf8_string"(), "is_utf8_string_loclen"(), and
               "is_utf8_string_loc"().

                       bool    is_ascii_string(const U8 *s, STRLEN len)

       is_utf8_char
               DEPRECATED!

               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 "is_utf8_char_buf" instead.

                       STRLEN  is_utf8_char(const U8 *s)

       is_utf8_char_buf
               Returns the number of bytes that comprise the first UTF-8 encoded character in
               buffer "buf".  "buf_end" should point to one position beyond the end of the
               buffer.  0 is returned if "buf" does not point to a complete, valid UTF-8 encoded
               character.

               Note that an INVARIANT character (i.e. ASCII on non-EBCDIC machines) is a valid
               UTF-8 character.

                       STRLEN  is_utf8_char_buf(const U8 *buf,
                                                const U8 *buf_end)

       is_utf8_string
               Returns true if the first "len" bytes of string "s" form a valid UTF-8 string,
               false otherwise.  If "len" is 0, it will be calculated using strlen(s) (which
               means if you use this option, that "s" has to have a terminating NUL byte).  Note
               that all characters being ASCII constitute 'a valid UTF-8 string'.

               See also "is_ascii_string"(), "is_utf8_string_loclen"(), and
               "is_utf8_string_loc"().

                       bool    is_utf8_string(const U8 *s, STRLEN len)

       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".

               See also "is_utf8_string_loclen"() and "is_utf8_string"().

                       bool    is_utf8_string_loc(const U8 *s, 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", and the number of UTF-8 encoded characters in the "el".

               See also "is_utf8_string_loc"() and "is_utf8_string"().

                       bool    is_utf8_string_loclen(const U8 *s, STRLEN len,
                                                     const U8 **ep, STRLEN *el)

       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.

                       char*   pv_uni_display(SV *dsv, const U8 *spv,
                                              STRLEN len, STRLEN pvlim,
                                              UV flags)

       sv_cat_decode
               The encoding is assumed to be an Encode object, the PV of the ssv is assumed to be
               octets in that encoding and decoding the input starts from the position which (PV
               + *offset) pointed to.  The dsv will be concatenated 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 the ssv.  The value which the offset points will be
               modified to the last input position on the 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
               The encoding is assumed to be an Encode object, on entry the PV of the sv is
               assumed to be octets in that encoding, and the sv will be converted into Unicode
               (and UTF-8).

               If the sv already is UTF-8 (or if it is not POK), or if the encoding is not a
               reference, nothing is done to the sv.  If the encoding is not an "Encode::XS"
               Encoding object, bad things will happen.  (See lib/encoding.pm and Encode.)

               The PV of the 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
               The "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.

               The "ustrp" is a pointer to the character buffer to put the conversion result to.
               The "lenp" is a pointer to the length of the result.

               The "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.  The "special" (usually, but not
               always, a multicharacter mapping), is tried first.

               The "special" is a string like "utf8::ToSpecLower", which means the hash
               %utf8::ToSpecLower.  The access to the hash is through Perl_to_utf8_case().

               The "normal" is a string like "ToLower" which means the swash %utf8::ToLower.

                       UV      to_utf8_case(const U8 *p, U8* ustrp,
                                            STRLEN *lenp, SV **swashp,
                                            const char *normal,
                                            const char *special)

       to_utf8_fold
               Convert the UTF-8 encoded character at "p" to its foldcase version and store that
               in UTF-8 in "ustrp" and its length in bytes in "lenp".  Note that the "ustrp"
               needs to be at least UTF8_MAXBYTES_CASE+1 bytes since the foldcase version may be
               longer than the original character (up to three characters).

               The first character of the foldcased version is returned (but note, as explained
               above, that there may be more.)

               The character at "p" is assumed by this routine to be well-formed.

                       UV      to_utf8_fold(const U8 *p, U8* ustrp,
                                            STRLEN *lenp)

       to_utf8_lower
               Convert the UTF-8 encoded character at "p" to its lowercase version and store that
               in UTF-8 in ustrp and its length in bytes in "lenp".  Note that the "ustrp" needs
               to be at least UTF8_MAXBYTES_CASE+1 bytes since the lowercase version may be
               longer than the original character.

               The first character of the lowercased version is returned (but note, as explained
               above, that there may be more.)

               The character at "p" is assumed by this routine to be well-formed.

                       UV      to_utf8_lower(const U8 *p, U8* ustrp,
                                             STRLEN *lenp)

       to_utf8_title
               Convert the UTF-8 encoded character at "p" to its titlecase version and store that
               in UTF-8 in "ustrp" and its length in bytes in "lenp".  Note that the "ustrp"
               needs to be at least UTF8_MAXBYTES_CASE+1 bytes since the titlecase version may be
               longer than the original character.

               The first character of the titlecased version is returned (but note, as explained
               above, that there may be more.)

               The character at "p" is assumed by this routine to be well-formed.

                       UV      to_utf8_title(const U8 *p, U8* ustrp,
                                             STRLEN *lenp)

       to_utf8_upper
               Convert the UTF-8 encoded character at "p" to its uppercase version and store that
               in UTF-8 in "ustrp" and its length in bytes in "lenp".  Note that the ustrp needs
               to be at least UTF8_MAXBYTES_CASE+1 bytes since the uppercase version may be
               longer than the original character.

               The first character of the uppercased version is returned (but note, as explained
               above, that there may be more.)

               The character at "p" is assumed by this routine to be well-formed.

                       UV      to_utf8_upper(const U8 *p, U8* ustrp,
                                             STRLEN *lenp)

       utf8n_to_uvchr
               Returns the native character value 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.

               "length" and "flags" are the same as "utf8n_to_uvuni"().

                       UV      utf8n_to_uvchr(const U8 *s, STRLEN curlen,
                                              STRLEN *retlen, U32 flags)

       utf8n_to_uvuni
               Bottom level UTF-8 decode routine.  Returns the 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, when a malformation is found, zero is
               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.

               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.  For allowed 0 length strings,
               this function returns 0; for allowed overlong sequences, the computed code point
               is returned; for all other allowed malformations, the Unicode REPLACEMENT
               CHARACTER is returned, as these have no determinable reasonable value.

               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.  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.

               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.  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.

               The flags UTF8_WARN_ILLEGAL_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.)

               Very large code points (above 0x7FFF_FFFF) are considered more problematic than
               the others that are above the Unicode legal maximum.  There are several reasons:
               they requre at least 32 bits to represent them on ASCII platforms, are not
               representable at all on EBCDIC platforms, and the original UTF-8 specification
               never went above this number (the current 0x10FFFF limit was imposed later).  (The
               smaller ones, those that fit into 32 bits, are representable by a UV on ASCII
               platforms, but not by an IV, which means that the number of operations that can be
               performed on them is quite restricted.)  The UTF-8 encoding on ASCII platforms for
               these large code points begins with a byte containing 0xFE or 0xFF.  The
               UTF8_DISALLOW_FE_FF flag will cause them to be treated as malformations, while
               allowing smaller above-Unicode code points.  (Of course UTF8_DISALLOW_SUPER will
               treat all above-Unicode code points, including these, as malformations.)
               Similarly, UTF8_WARN_FE_FF acts just like the other WARN flags, but applies just
               to these code points.

               All other code points corresponding to Unicode characters, including private use
               and those yet to be assigned, are never considered malformed and never warn.

               Most code should use "utf8_to_uvchr_buf"() rather than call this directly.

                       UV      utf8n_to_uvuni(const U8 *s, STRLEN curlen,
                                              STRLEN *retlen, U32 flags)

       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, I32 off)

       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
               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".

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

                       U8*     utf8_to_bytes(U8 *s, STRLEN *len)

       utf8_to_uvchr
               DEPRECATED!

               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_uvuni" for details on when the
               REPLACEMENT CHARACTER is returned.

                       UV      utf8_to_uvchr(const U8 *s, STRLEN *retlen)

       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_uvuni" for details on
               when the REPLACEMENT CHARACTER is returned.

                       UV      utf8_to_uvchr_buf(const U8 *s, const U8 *send,
                                                 STRLEN *retlen)

       utf8_to_uvuni
               DEPRECATED!

               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.

               This function should only be used when the returned UV is considered an index into
               the Unicode semantic tables (e.g. swashes).

               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_uvuni_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" 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_uvuni" for details on
               when the REPLACEMENT CHARACTER is returned.

                       UV      utf8_to_uvuni(const U8 *s, STRLEN *retlen)

       utf8_to_uvuni_buf
               Returns the Unicode 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.

               This function should only be used when the returned UV is considered an index into
               the Unicode semantic tables (e.g. swashes).

               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_uvuni" for details on
               when the REPLACEMENT CHARACTER is returned.

                       UV      utf8_to_uvuni_buf(const U8 *s, const U8 *send,
                                                 STRLEN *retlen)

       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 "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;

                       U8*     uvchr_to_utf8(U8 *d, UV uv)

       uvuni_to_utf8_flags
               Adds the UTF-8 representation of the Unicode code point "uv" to the end of the
               string "d"; "d" should have at least "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 = uvuni_to_utf8_flags(d, uv, flags);

               or, in most cases,

                   d = uvuni_to_utf8(d, uv);

               (which is equivalent to)

                   d = uvuni_to_utf8_flags(d, uv, 0);

               This is the recommended Unicode-aware way of saying

                   *(d++) = uv;

               where uv is a code point expressed in Latin-1 or above, not the platform's native
               character set.  Almost all code should instead use "uvchr_to_utf8" or
               "uvchr_to_utf8_flags".

               This function will convert to UTF-8 (and not warn) even code points that aren't
               legal Unicode or are problematic, unless "flags" contains one or more of the
               following flags:

               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.

               The UNICODE_WARN_NONCHAR and UNICODE_DISALLOW_NONCHAR flags correspondingly 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.  Code points above
               0x7FFF_FFFF (which are even less portable) can be warned and/or disallowed even if
               other above-Unicode code points are accepted by the UNICODE_WARN_FE_FF and
               UNICODE_DISALLOW_FE_FF flags.

               And finally, the flag UNICODE_WARN_ILLEGAL_INTERCHANGE selects all four of the
               above WARN flags; and UNICODE_DISALLOW_ILLEGAL_INTERCHANGE selects all four
               DISALLOW flags.

                       U8*     uvuni_to_utf8_flags(U8 *d, UV uv, UV flags)

Variables created by "xsubpp" and "xsubpp" 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

       newXSproto
               Used by "xsubpp" to hook up XSUBs as Perl subs.  Adds Perl prototypes to the subs.

       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_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_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.

       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

       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 use one of the undocumented functions below, you may wish to consider creating and
       submitting documentation for it. If your patch is accepted, this will indicate that the
       interface is stable (unless it is explicitly marked otherwise).

       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
       clone_params_del
       clone_params_new
       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_all
       dump_eval
       dump_fds
       dump_form
       dump_indent
       dump_mstats
       dump_packsubs
       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_p
       hv_placeholders_set
       hv_rand_set
       hv_riter_p
       hv_riter_set
       init_global_struct
       init_i18nl10n
       init_i18nl14n
       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_htonl
       my_lstat
       my_memcmp
       my_memset
       my_ntohl
       my_pclose
       my_popen
       my_popen_list
       my_setenv
       my_socketpair
       my_stat
       my_strftime
       my_strlcat
       my_strlcpy
       my_swap
       newANONATTRSUB
       newANONHASH
       newANONLIST
       newANONSUB
       newATTRSUB
       newAVREF
       newCVREF
       newFORM
       newGVREF
       newGVgen
       newGVgen_flags
       newHVREF
       newHVhv
       newIO
       newMYSUB
       newPROG
       newRV
       newSUB
       newSVREF
       newSVpvf_nocontext
       new_collate
       new_ctype
       new_numeric
       new_stackinfo
       ninstr
       op_dump
       op_free
       op_null
       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_clear
       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
       regclass_swash
       regdump
       regdupe_internal
       regexec_flags
       regfree_internal
       reginitcolors
       regnext
       repeatcpy
       rninstr
       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_gp
       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
       screaminstr
       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_dump
       sv_dup
       sv_dup_inc
       sv_peek
       sv_pvn_nomg
       sv_setpvf_mg_nocontext
       sv_setpvf_nocontext
       sv_utf8_upgrade_flags_grow
       swash_fetch
       swash_init
       sys_init
       sys_init3
       sys_intern_clear
       sys_intern_dup
       sys_intern_init
       sys_term
       taint_env
       taint_proper
       tmps_grow
       unlnk
       unsharepvn
       utf16_to_utf8
       utf16_to_utf8_reversed
       uvchr_to_utf8_flags
       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

POD ERRORS

       Hey! The above document had some coding errors, which are explained below:

       Around line 8556:
           Unterminated C<...> sequence