Ubuntu Manpage: perl58delta - what is new for perl v5.8.0

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NAME

       perl58delta - what is new for perl v5.8.0

DESCRIPTION

       This document describes differences between the 5.6.0 release and the 5.8.0 release.

       Many of the bug fixes in 5.8.0 were already seen in the 5.6.1 maintenance release since
       the two releases were kept closely coordinated (while 5.8.0 was still called
       5.7.something).

       Changes that were integrated into the 5.6.1 release are marked "[561]".  Many of these
       changes have been further developed since 5.6.1 was released, those are marked "[561+]".

       You can see the list of changes in the 5.6.1 release (both from the 5.005_03 release and
       the 5.6.0 release) by reading perl561delta.

Highlights In 5.8.0

       •   Better Unicode support

       •   New IO Implementation

       •   New Thread Implementation

       •   Better Numeric Accuracy

       •   Safe Signals

       •   Many New Modules

       •   More Extensive Regression Testing

Incompatible Changes

   Binary Incompatibility
       Perl 5.8 is not binary compatible with earlier releases of Perl.

       You have to recompile your XS modules.

       (Pure Perl modules should continue to work.)

       The major reason for the discontinuity is the new IO architecture called PerlIO.  PerlIO
       is the default configuration because without it many new features of Perl 5.8 cannot be
       used.  In other words: you just have to recompile your modules containing XS code, sorry
       about that.

       In future releases of Perl, non-PerlIO aware XS modules may become completely unsupported.
       This shouldn't be too difficult for module authors, however: PerlIO has been designed as a
       drop-in replacement (at the source code level) for the stdio interface.

       Depending on your platform, there are also other reasons why we decided to break binary
       compatibility, please read on.

   64-bit platforms and malloc
       If your pointers are 64 bits wide, the Perl malloc is no longer being used because it does
       not work well with 8-byte pointers.  Also, usually the system mallocs on such platforms
       are much better optimized for such large memory models than the Perl malloc.  Some memory-
       hungry Perl applications like the PDL don't work well with Perl's malloc.  Finally, other
       applications than Perl (such as mod_perl) tend to prefer the system malloc.  Such
       platforms include Alpha and 64-bit HPPA, MIPS, PPC, and Sparc.

   AIX Dynaloading
       The AIX dynaloading now uses in AIX releases 4.3 and newer the native dlopen interface of
       AIX instead of the old emulated interface.  This change will probably break backward
       compatibility with compiled modules.  The change was made to make Perl more compliant with
       other applications like mod_perl which are using the AIX native interface.

   Attributes for "my" variables now handled at run-time
       The "my EXPR : ATTRS" syntax now applies variable attributes at run-time.  (Subroutine and
       "our" variables still get attributes applied at compile-time.)  See attributes for
       additional details.  In particular, however, this allows variable attributes to be useful
       for "tie" interfaces, which was a deficiency of earlier releases.  Note that the new
       semantics doesn't work with the Attribute::Handlers module (as of version 0.76).

   Socket Extension Dynamic in VMS
       The Socket extension is now dynamically loaded instead of being statically built in.  This
       may or may not be a problem with ancient TCP/IP stacks of VMS: we do not know since we
       weren't able to test Perl in such configurations.

   IEEE-format Floating Point Default on OpenVMS Alpha
       Perl now uses IEEE format (T_FLOAT) as the default internal floating point format on
       OpenVMS Alpha, potentially breaking binary compatibility with external libraries or
       existing data.  G_FLOAT is still available as a configuration option.  The default on VAX
       (D_FLOAT) has not changed.

   New Unicode Semantics (no more "use utf8", almost)
       Previously in Perl 5.6 to use Unicode one would say "use utf8" and then the operations
       (like string concatenation) were Unicode-aware in that lexical scope.

       This was found to be an inconvenient interface, and in Perl 5.8 the Unicode model has
       completely changed: now the "Unicodeness" is bound to the data itself, and for most of the
       time "use utf8" is not needed at all.  The only remaining use of "use utf8" is when the
       Perl script itself has been written in the UTF-8 encoding of Unicode.  (UTF-8 has not been
       made the default since there are many Perl scripts out there that are using various
       national eight-bit character sets, which would be illegal in UTF-8.)

       See perluniintro for the explanation of the current model, and utf8 for the current use of
       the utf8 pragma.

   New Unicode Properties
       Unicode scripts are now supported. Scripts are similar to (and superior to) Unicode
       blocks. The difference between scripts and blocks is that scripts are the glyphs used by a
       language or a group of languages, while the blocks are more artificial groupings of
       (mostly) 256 characters based on the Unicode numbering.

       In general, scripts are more inclusive, but not universally so. For example, while the
       script "Latin" includes all the Latin characters and their various diacritic-adorned
       versions, it does not include the various punctuation or digits (since they are not solely
       "Latin").

       A number of other properties are now supported, including "\p{L&}", "\p{Any}"
       "\p{Assigned}", "\p{Unassigned}", "\p{Blank}" [561] and "\p{SpacePerl}" [561] (along with
       their "\P{...}" versions, of course).  See perlunicode for details, and more additions.

       The "In" or "Is" prefix to names used with the "\p{...}" and "\P{...}" are now almost
       always optional. The only exception is that a "In" prefix is required to signify a Unicode
       block when a block name conflicts with a script name. For example, "\p{Tibetan}" refers to
       the script, while "\p{InTibetan}" refers to the block. When there is no name conflict, you
       can omit the "In" from the block name (e.g. "\p{BraillePatterns}"), but to be safe, it's
       probably best to always use the "In").

   REF(...) Instead Of SCALAR(...)
       A reference to a reference now stringifies as "REF(0x81485ec)" instead of
       "SCALAR(0x81485ec)" in order to be more consistent with the return value of ref().

   pack/unpack D/F recycled
       The undocumented pack/unpack template letters D/F have been recycled for better use: now
       they stand for long double (if supported by the platform) and NV (Perl internal floating
       point type).  (They used to be aliases for d/f, but you never knew that.)

   glob() now returns filenames in alphabetical order
       The list of filenames from glob() (or <...>) is now by default sorted alphabetically to be
       csh-compliant (which is what happened before in most Unix platforms).  (bsd_glob() does
       still sort platform natively, ASCII or EBCDIC, unless GLOB_ALPHASORT is specified.) [561]

   Deprecations
       •   The semantics of bless(REF, REF) were unclear and until someone proves it to make some
           sense, it is forbidden.

       •   The obsolete chat2 library that should never have been allowed to escape the
           laboratory has been decommissioned.

       •   Using chdir("") or chdir(undef) instead of explicit chdir() is doubtful.  A failure
           (think chdir(some_function()) can lead into unintended chdir() to the home directory,
           therefore this behaviour is deprecated.

       •   The builtin dump() function has probably outlived most of its usefulness.  The core-
           dumping functionality will remain in future available as an explicit call to
           "CORE::dump()", but in future releases the behaviour of an unqualified "dump()" call
           may change.

       •   The very dusty examples in the eg/ directory have been removed.  Suggestions for new
           shiny examples welcome but the main issue is that the examples need to be documented,
           tested and (most importantly) maintained.

       •   The (bogus) escape sequences \8 and \9 now give an optional warning ("Unrecognized
           escape passed through").  There is no need to \-escape any "\w" character.

       •   The *glob{FILEHANDLE} is deprecated, use *glob{IO} instead.

       •   The "package;" syntax ("package" without an argument) has been deprecated.  Its
           semantics were never that clear and its implementation even less so.  If you have used
           that feature to disallow all but fully qualified variables, "use strict;" instead.

       •   The unimplemented POSIX regex features [[.cc.]] and [[=c=]] are still recognised but
           now cause fatal errors.  The previous behaviour of ignoring them by default and
           warning if requested was unacceptable since it, in a way, falsely promised that the
           features could be used.

       •   In future releases, non-PerlIO aware XS modules may become completely unsupported.
           Since PerlIO is a drop-in replacement for stdio at the source code level, this
           shouldn't be that drastic a change.

       •   Previous versions of perl and some readings of some sections of Camel III implied that
           the ":raw" "discipline" was the inverse of ":crlf".  Turning off "clrfness" is no
           longer enough to make a stream truly binary. So the PerlIO ":raw" layer (or
           "discipline", to use the Camel book's older terminology) is now formally defined as
           being equivalent to binmode(FH) - which is in turn defined as doing whatever is
           necessary to pass each byte as-is without any translation.  In particular binmode(FH)
           - and hence ":raw" - will now turn off both CRLF and UTF-8 translation and remove
           other layers (e.g. :encoding()) which would modify byte stream.

       •   The current user-visible implementation of pseudo-hashes (the weird use of the first
           array element) is deprecated starting from Perl 5.8.0 and will be removed in Perl
           5.10.0, and the feature will be implemented differently.  Not only is the current
           interface rather ugly, but the current implementation slows down normal array and hash
           use quite noticeably. The "fields" pragma interface will remain available.  The
           restricted hashes interface is expected to be the replacement interface (see
           Hash::Util).  If your existing programs depends on the underlying implementation,
           consider using Class::PseudoHash from CPAN.

       •   The syntaxes "@a->[...]" and  "%h->{...}" have now been deprecated.

       •   After years of trying, suidperl is considered to be too complex to ever be considered
           truly secure.  The suidperl functionality is likely to be removed in a future release.

       •   The 5.005 threads model (module "Thread") is deprecated and expected to be removed in
           Perl 5.10.  Multithreaded code should be migrated to the new ithreads model (see
           threads, threads::shared and perlthrtut).

       •   The long deprecated uppercase aliases for the string comparison operators (EQ, NE, LT,
           LE, GE, GT) have now been removed.

       •   The tr///C and tr///U features have been removed and will not return; the interface
           was a mistake.  Sorry about that.  For similar functionality, see pack('U0', ...) and
           pack('C0', ...). [561]

       •   Earlier Perls treated "sub foo (@bar)" as equivalent to "sub foo (@)".  The prototypes
           are now checked better at compile-time for invalid syntax.  An optional warning is
           generated ("Illegal character in prototype...")  but this may be upgraded to a fatal
           error in a future release.

       •   The "exec LIST" and "system LIST" operations now produce warnings on tainted data and
           in some future release they will produce fatal errors.

       •   The existing behaviour when localising tied arrays and hashes is wrong, and will be
           changed in a future release, so do not rely on the existing behaviour. See "Localising
           Tied Arrays and Hashes Is Broken".

Core Enhancements

   Unicode Overhaul
       Unicode in general should be now much more usable than in Perl 5.6.0 (or even in 5.6.1).
       Unicode can be used in hash keys, Unicode in regular expressions should work now, Unicode
       in tr/// should work now, Unicode in I/O should work now.  See perluniintro for
       introduction and perlunicode for details.

       •   The Unicode Character Database coming with Perl has been upgraded to Unicode 3.2.0.
           For more information, see http://www.unicode.org/ .  [561+] (5.6.1 has UCD 3.0.1.)

       •   For developers interested in enhancing Perl's Unicode capabilities: almost all the UCD
           files are included with the Perl distribution in the lib/unicore subdirectory.  The
           most notable omission, for space considerations, is the Unihan database.

       •   The properties \p{Blank} and \p{SpacePerl} have been added. "Blank" is like C
           isblank(), that is, it contains only "horizontal whitespace" (the space character is,
           the newline isn't), and the "SpacePerl" is the Unicode equivalent of "\s" (\p{Space}
           isn't, since that includes the vertical tabulator character, whereas "\s" doesn't.)

           See "New Unicode Properties" earlier in this document for additional information on
           changes with Unicode properties.

   PerlIO is Now The Default
       •   IO is now by default done via PerlIO rather than system's "stdio".  PerlIO allows
           "layers" to be "pushed" onto a file handle to alter the handle's behaviour.  Layers
           can be specified at open time via 3-arg form of open:

              open($fh,'>:crlf :utf8', $path) || ...

           or on already opened handles via extended "binmode":

              binmode($fh,':encoding(iso-8859-7)');

           The built-in layers are: unix (low level read/write), stdio (as in previous Perls),
           perlio (re-implementation of stdio buffering in a portable manner), crlf (does CRLF
           <=> "\n" translation as on Win32, but available on any platform).  A mmap layer may be
           available if platform supports it (mostly Unixes).

           Layers to be applied by default may be specified via the 'open' pragma.

           See "Installation and Configuration Improvements" for the effects of PerlIO on your
           architecture name.

       •   If your platform supports fork(), you can use the list form of "open" for pipes.  For
           example:

               open KID_PS, "-|", "ps", "aux" or die $!;

           forks the ps(1) command (without spawning a shell, as there are more than three
           arguments to open()), and reads its standard output via the "KID_PS" filehandle.  See
           perlipc.

       •   File handles can be marked as accepting Perl's internal encoding of Unicode (UTF-8 or
           UTF-EBCDIC depending on platform) by a pseudo layer ":utf8" :

              open($fh,">:utf8","Uni.txt");

           Note for EBCDIC users: the pseudo layer ":utf8" is erroneously named for you since
           it's not UTF-8 what you will be getting but instead UTF-EBCDIC.  See perlunicode,
           utf8, and http://www.unicode.org/reports/tr16/ for more information.  In future
           releases this naming may change.  See perluniintro for more information about UTF-8.

       •   If your environment variables (LC_ALL, LC_CTYPE, LANG) look like you want to use UTF-8
           (any of the variables match "/utf-?8/i"), your STDIN, STDOUT, STDERR handles and the
           default open layer (see open) are marked as UTF-8.  (This feature, like other new
           features that combine Unicode and I/O, work only if you are using PerlIO, but that's
           the default.)

           Note that after this Perl really does assume that everything is UTF-8: for example if
           some input handle is not, Perl will probably very soon complain about the input data
           like this "Malformed UTF-8 ..." since any old eight-bit data is not legal UTF-8.

           Note for code authors: if you want to enable your users to use UTF-8 as their default
           encoding  but in your code still have eight-bit I/O streams (such as images or zip
           files), you need to explicitly open() or binmode() with ":bytes" (see "open" in
           perlfunc and "binmode" in perlfunc), or you can just use "binmode(FH)" (nice for
           pre-5.8.0 backward compatibility).

       •   File handles can translate character encodings from/to Perl's internal Unicode form on
           read/write via the ":encoding()" layer.

       •   File handles can be opened to "in memory" files held in Perl scalars via:

              open($fh,'>', \$variable) || ...

       •   Anonymous temporary files are available without need to 'use FileHandle' or other
           module via

              open($fh,"+>", undef) || ...

           That is a literal undef, not an undefined value.

   ithreads
       The new interpreter threads ("ithreads" for short) implementation of multithreading, by
       Arthur Bergman, replaces the old "5.005 threads" implementation.  In the ithreads model
       any data sharing between threads must be explicit, as opposed to the model where data
       sharing was implicit.  See threads and threads::shared, and perlthrtut.

       As a part of the ithreads implementation Perl will also use any necessary and detectable
       reentrant libc interfaces.

   Restricted Hashes
       A restricted hash is restricted to a certain set of keys, no keys outside the set can be
       added.  Also individual keys can be restricted so that the key cannot be deleted and the
       value cannot be changed.  No new syntax is involved: the Hash::Util module is the
       interface.

   Safe Signals
       Perl used to be fragile in that signals arriving at inopportune moments could corrupt
       Perl's internal state.  Now Perl postpones handling of signals until it's safe (between
       opcodes).

       This change may have surprising side effects because signals no longer interrupt Perl
       instantly.  Perl will now first finish whatever it was doing, like finishing an internal
       operation (like sort()) or an external operation (like an I/O operation), and only then
       look at any arrived signals (and before starting the next operation).  No more corrupt
       internal state since the current operation is always finished first, but the signal may
       take more time to get heard.  Note that breaking out from potentially blocking operations
       should still work, though.

   Understanding of Numbers
       In general a lot of fixing has happened in the area of Perl's understanding of numbers,
       both integer and floating point.  Since in many systems the standard number parsing
       functions like "strtoul()" and "atof()" seem to have bugs, Perl tries to work around their
       deficiencies.  This results hopefully in more accurate numbers.

       Perl now tries internally to use integer values in numeric conversions and basic
       arithmetics (+ - * /) if the arguments are integers, and tries also to keep the results
       stored internally as integers.  This change leads to often slightly faster and always less
       lossy arithmetics. (Previously Perl always preferred floating point numbers in its math.)

   Arrays now always interpolate into double-quoted strings [561]
       In double-quoted strings, arrays now interpolate, no matter what.  The behavior in earlier
       versions of perl 5 was that arrays would interpolate into strings if the array had been
       mentioned before the string was compiled, and otherwise Perl would raise a fatal compile-
       time error.  In versions 5.000 through 5.003, the error was

               Literal @example now requires backslash

       In versions 5.004_01 through 5.6.0, the error was

               In string, @example now must be written as \@example

       The idea here was to get people into the habit of writing "fred\@example.com" when they
       wanted a literal "@" sign, just as they have always written "Give me back my \$5" when
       they wanted a literal "$" sign.

       Starting with 5.6.1, when Perl now sees an "@" sign in a double-quoted string, it always
       attempts to interpolate an array, regardless of whether or not the array has been used or
       declared already.  The fatal error has been downgraded to an optional warning:

               Possible unintended interpolation of @example in string

       This warns you that "fred@example.com" is going to turn into "fred.com" if you don't
       backslash the "@".  See http://perl.plover.com/at-error.html for more details about the
       history here.

   Miscellaneous Changes
       •   AUTOLOAD is now lvaluable, meaning that you can add the :lvalue attribute to AUTOLOAD
           subroutines and you can assign to the AUTOLOAD return value.

       •   The $Config{byteorder} (and corresponding BYTEORDER in config.h) was previously wrong
           in platforms if sizeof(long) was 4, but sizeof(IV) was 8.  The byteorder was only
           sizeof(long) bytes long (1234 or 4321), but now it is correctly sizeof(IV) bytes long,
           (12345678 or 87654321).  (This problem didn't affect Windows platforms.)

           Also, $Config{byteorder} is now computed dynamically--this is more robust with "fat
           binaries" where an executable image contains binaries for more than one binary
           platform, and when cross-compiling.

       •   "perl -d:Module=arg,arg,arg" now works (previously one couldn't pass in multiple
           arguments.)

       •   "do" followed by a bareword now ensures that this bareword isn't a keyword (to avoid a
           bug where "do q(foo.pl)" tried to call a subroutine called "q").  This means that for
           example instead of "do format()" you must write "do &format()".

       •   The builtin dump() now gives an optional warning "dump() better written as
           CORE::dump()", meaning that by default "dump(...)" is resolved as the builtin dump()
           which dumps core and aborts, not as (possibly) user-defined "sub dump".  To call the
           latter, qualify the call as "&dump(...)".  (The whole dump() feature is to considered
           deprecated, and possibly removed/changed in future releases.)

       •   chomp() and chop() are now overridable.  Note, however, that their prototype (as given
           by "prototype("CORE::chomp")" is undefined, because it cannot be expressed and
           therefore one cannot really write replacements to override these builtins.

       •   END blocks are now run even if you exit/die in a BEGIN block.  Internally, the
           execution of END blocks is now controlled by PL_exit_flags & PERL_EXIT_DESTRUCT_END.
           This enables the new behaviour for Perl embedders. This will default in 5.10. See
           perlembed.

       •   Formats now support zero-padded decimal fields.

       •   Although "you shouldn't do that", it was possible to write code that depends on Perl's
           hashed key order (Data::Dumper does this).  The new algorithm "One-at-a-Time" produces
           a different hashed key order.  More details are in "Performance Enhancements".

       •   lstat(FILEHANDLE) now gives a warning because the operation makes no sense.  In future
           releases this may become a fatal error.

       •   Spurious syntax errors generated in certain situations, when glob() caused File::Glob
           to be loaded for the first time, have been fixed. [561]

       •   Lvalue subroutines can now return "undef" in list context.  However, the lvalue
           subroutine feature still remains experimental.  [561+]

       •   A lost warning "Can't declare ... dereference in my" has been restored (Perl had it
           earlier but it became lost in later releases.)

       •   A new special regular expression variable has been introduced: $^N, which contains the
           most-recently closed group (submatch).

       •   "no Module;" does not produce an error even if Module does not have an unimport()
           method.  This parallels the behavior of "use" vis-a-vis "import". [561]

       •   The numerical comparison operators return "undef" if either operand is a NaN.
           Previously the behaviour was unspecified.

       •   "our" can now have an experimental optional attribute "unique" that affects how global
           variables are shared among multiple interpreters, see "our" in perlfunc.

       •   The following builtin functions are now overridable: each(), keys(), pop(), push(),
           shift(), splice(), unshift(). [561]

       •   "pack() / unpack()" can now group template letters with "()" and then apply
           repetition/count modifiers on the groups.

       •   "pack() / unpack()" can now process the Perl internal numeric types: IVs, UVs, NVs--
           and also long doubles, if supported by the platform.  The template letters are "j",
           "J", "F", and "D".

       •   "pack('U0a*', ...)" can now be used to force a string to UTF-8.

       •   my __PACKAGE__ $obj now works. [561]

       •   POSIX::sleep() now returns the number of unslept seconds (as the POSIX standard says),
           as opposed to CORE::sleep() which returns the number of slept seconds.

       •   printf() and sprintf() now support parameter reordering using the "%\d+\$" and
           "*\d+\$" syntaxes.  For example

               printf "%2\$s %1\$s\n", "foo", "bar";

           will print "bar foo\n".  This feature helps in writing internationalised software, and
           in general when the order of the parameters can vary.

       •   The (\&) prototype now works properly. [561]

       •   prototype(\[$@%&]) is now available to implicitly create references (useful for
           example if you want to emulate the tie() interface).

       •   A new command-line option, "-t" is available.  It is the little brother of "-T":
           instead of dying on taint violations, lexical warnings are given.  This is only meant
           as a temporary debugging aid while securing the code of old legacy applications.  This
           is not a substitute for -T.

       •   In other taint news, the "exec LIST" and "system LIST" have now been considered too
           risky (think "exec @ARGV": it can start any program with any arguments), and now the
           said forms cause a warning under lexical warnings.  You should carefully launder the
           arguments to guarantee their validity.  In future releases of Perl the forms will
           become fatal errors so consider starting laundering now.

       •   Tied hash interfaces are now required to have the EXISTS and DELETE methods (either
           own or inherited).

       •   If tr/// is just counting characters, it doesn't attempt to modify its target.

       •   untie() will now call an UNTIE() hook if it exists.  See perltie for details. [561]

       •   "utime" in perlfunc now supports "utime undef, undef, @files" to change the file
           timestamps to the current time.

       •   The rules for allowing underscores (underbars) in numeric constants have been relaxed
           and simplified: now you can have an underscore simply between digits.

       •   Rather than relying on C's argv[0] (which may not contain a full pathname) where
           possible $^X is now set by asking the operating system.  (eg by reading /proc/self/exe
           on Linux, /proc/curproc/file on FreeBSD)

       •   A new variable, "${^TAINT}", indicates whether taint mode is enabled.

       •   You can now override the readline() builtin, and this overrides also the <FILEHANDLE>
           angle bracket operator.

       •   The command-line options -s and -F are now recognized on the shebang (#!) line.

       •   Use of the "/c" match modifier without an accompanying "/g" modifier elicits a new
           warning: "Use of /c modifier is meaningless without /g".

           Use of "/c" in substitutions, even with "/g", elicits "Use of /c modifier is
           meaningless in s///".

           Use of "/g" with "split" elicits "Use of /g modifier is meaningless in split".

       •   Support for the "CLONE" special subroutine had been added.  With ithreads, when a new
           thread is created, all Perl data is cloned, however non-Perl data cannot be cloned
           automatically.  In "CLONE" you can do whatever you need to do, like for example handle
           the cloning of non-Perl data, if necessary.  "CLONE" will be executed once for every
           package that has it defined or inherited.  It will be called in the context of the new
           thread, so all modifications are made in the new area.

           See perlmod

Modules and Pragmata

New Modules and Pragmata
• "Attribute::Handlers", originally by Damian Conway and now maintained by Arthur
Bergman, allows a class to define attribute handlers.

package MyPack;
use Attribute::Handlers;
sub Wolf :ATTR(SCALAR) { print "howl!\n" }

# later, in some package using or inheriting from MyPack...

my MyPack $Fluffy : Wolf; # the attribute handler Wolf will be called

Both variables and routines can have attribute handlers. Handlers can be specific to
type (SCALAR, ARRAY, HASH, or CODE), or specific to the exact compilation phase
(BEGIN, CHECK, INIT, or END). See Attribute::Handlers.

• "B::Concise", by Stephen McCamant, is a new compiler backend for walking the Perl
syntax tree, printing concise info about ops. The output is highly customisable. See
B::Concise. [561+]

• The new bignum, bigint, and bigrat pragmas, by Tels, implement transparent bignum
support (using the Math::BigInt, Math::BigFloat, and Math::BigRat backends).

• "Class::ISA", by Sean Burke, is a module for reporting the search path for a class's
ISA tree. See Class::ISA.

• "Cwd" now has a split personality: if possible, an XS extension is used, (this will
hopefully be faster, more secure, and more robust) but if not possible, the familiar
Perl implementation is used.

• "Devel::PPPort", originally by Kenneth Albanowski and now maintained by Paul Marquess,
has been added. It is primarily used by "h2xs" to enhance portability of XS modules
between different versions of Perl. See Devel::PPPort.

• "Digest", frontend module for calculating digests (checksums), from Gisle Aas, has
been added. See Digest.

• "Digest::MD5" for calculating MD5 digests (checksums) as defined in RFC 1321, from
Gisle Aas, has been added. See Digest::MD5.

use Digest::MD5 'md5_hex';

$digest = md5_hex("Thirsty Camel");

print $digest, "\n"; # 01d19d9d2045e005c3f1b80e8b164de1

NOTE: the "MD5" backward compatibility module is deliberately not included since its
further use is discouraged.

Utility Changes

• Emacs perl mode (emacs/cperl-mode.el) has been updated to version 4.31.

• emacs/e2ctags.pl is now much faster.

• "enc2xs" is a tool for people adding their own encodings to the Encode module.

• "h2ph" now supports C trigraphs.

• "h2xs" now produces a template README.

• "h2xs" now uses "Devel::PPPort" for better portability between different versions of
Perl.

• "h2xs" uses the new ExtUtils::Constant module which will affect newly created
extensions that define constants. Since the new code is more correct (if you have two
constants where the first one is a prefix of the second one, the first constant never
got defined), less lossy (it uses integers for integer constant, as opposed to the old
code that used floating point numbers even for integer constants), and slightly
faster, you might want to consider regenerating your extension code (the new scheme
makes regenerating easy). h2xs now also supports C trigraphs.

• "libnetcfg" has been added to configure libnet.

• "perlbug" is now much more robust. It also sends the bug report to perl.org, not
perl.com.

• "perlcc" has been rewritten and its user interface (that is, command line) is much
more like that of the Unix C compiler, cc. (The perlbc tools has been removed. Use
"perlcc -B" instead.) Note that perlcc is still considered very experimental and
unsupported. [561]

• "perlivp" is a new Installation Verification Procedure utility for running any time
after installing Perl.

• "piconv" is an implementation of the character conversion utility "iconv",
demonstrating the new Encode module.

• "pod2html" now allows specifying a cache directory.

• "pod2html" now produces XHTML 1.0.

• "pod2html" now understands POD written using different line endings (PC-like CRLF
versus Unix-like LF versus MacClassic-like CR).

• "s2p" has been completely rewritten in Perl. (It is in fact a full implementation of
sed in Perl: you can use the sed functionality by using the "psed" utility.)

• "xsubpp" now understands POD documentation embedded in the *.xs files. [561]

• "xsubpp" now supports the OUT keyword.

New Documentation

• perl56delta details the changes between the 5.005 release and the 5.6.0 release.

• perlclib documents the internal replacements for standard C library functions.
(Interesting only for extension writers and Perl core hackers.) [561+]

• perldebtut is a Perl debugging tutorial. [561+]

• perlebcdic contains considerations for running Perl on EBCDIC platforms. [561+]

• perlintro is a gentle introduction to Perl.

• perliol documents the internals of PerlIO with layers.

• perlmodstyle is a style guide for writing modules.

• perlnewmod tells about writing and submitting a new module. [561+]

• perlpacktut is a pack() tutorial.

• perlpod has been rewritten to be clearer and to record the best practices gathered
over the years.

• perlpodspec is a more formal specification of the pod format, mainly of interest for
writers of pod applications, not to people writing in pod.

• perlretut is a regular expression tutorial. [561+]

• perlrequick is a regular expressions quick-start guide. Yes, much quicker than
perlretut. [561]

• perltodo has been updated.

• perltootc has been renamed as perltooc (to not to conflict with perltoot in
filesystems restricted to "8.3" names).

• perluniintro is an introduction to using Unicode in Perl. (perlunicode is more of a
detailed reference and background information)

• perlutil explains the command line utilities packaged with the Perl distribution.
[561+]

The following platform-specific documents are available before the installation as
README.platform, and after the installation as perlplatform:

perlaix perlamiga perlapollo perlbeos perlbs2000
perlce perlcygwin perldgux perldos perlepoc perlfreebsd perlhpux
perlhurd perlirix perlmachten perlmacos perlmint perlmpeix
perlnetware perlos2 perlos390 perlplan9 perlqnx perlsolaris
perltru64 perluts perlvmesa perlvms perlvos perlwin32

These documents usually detail one or more of the following subjects: configuring,
building, testing, installing, and sometimes also using Perl on the said platform.

Eastern Asian Perl users are now welcomed in their own languages: README.jp (Japanese),
README.ko (Korean), README.cn (simplified Chinese) and README.tw (traditional Chinese),
which are written in normal pod but encoded in EUC-JP, EUC-KR, EUC-CN and Big5. These
will get installed as

perljp perlko perlcn perltw

• The documentation for the POSIX-BC platform is called "BS2000", to avoid confusion
with the Perl POSIX module.

• The documentation for the WinCE platform is called perlce (README.ce in the source
code kit), to avoid confusion with the perlwin32 documentation on 8.3-restricted
filesystems.

Performance Enhancements

• map() could get pathologically slow when the result list it generates is larger than
the source list. The performance has been improved for common scenarios. [561]

• sort() is also fully reentrant, in the sense that the sort function can itself call
sort(). This did not work reliably in previous releases. [561]

• sort() has been changed to use primarily mergesort internally as opposed to the
earlier quicksort. For very small lists this may result in slightly slower sorting
times, but in general the speedup should be at least 20%. Additional bonuses are that
the worst case behaviour of sort() is now better (in computer science terms it now
runs in time O(N log N), as opposed to quicksort's Theta(N**2) worst-case run time
behaviour), and that sort() is now stable (meaning that elements with identical keys
will stay ordered as they were before the sort). See the "sort" pragma for
information.

The story in more detail: suppose you want to serve yourself a little slice of Pi.

@digits = ( 3,1,4,1,5,9 );

A numerical sort of the digits will yield (1,1,3,4,5,9), as expected. Which 1 comes
first is hard to know, since one 1 looks pretty much like any other. You can regard
this as totally trivial, or somewhat profound. However, if you just want to sort the
even digits ahead of the odd ones, then what will

sort { ($a % 2) <=> ($b % 2) } @digits;

yield? The only even digit, 4, will come first. But how about the odd numbers, which
all compare equal? With the quicksort algorithm used to implement Perl 5.6 and
earlier, the order of ties is left up to the sort. So, as you add more and more
digits of Pi, the order in which the sorted even and odd digits appear will change.
and, for sufficiently large slices of Pi, the quicksort algorithm in Perl 5.8 won't
return the same results even if reinvoked with the same input. The justification for
this rests with quicksort's worst case behavior. If you run

sort { $a <=> $b } ( 1 .. $N , 1 .. $N );

(something you might approximate if you wanted to merge two sorted arrays using sort),
doubling $N doesn't just double the quicksort time, it quadruples it. Quicksort has a
worst case run time that can grow like N**2, so-called quadratic behaviour, and it can
happen on patterns that may well arise in normal use. You won't notice this for small
arrays, but you will notice it with larger arrays, and you may not live long enough
for the sort to complete on arrays of a million elements. So the 5.8 quicksort
scrambles large arrays before sorting them, as a statistical defence against quadratic
behaviour. But that means if you sort the same large array twice, ties may be broken
in different ways.

Because of the unpredictability of tie-breaking order, and the quadratic worst-case
behaviour, quicksort was almost replaced completely with a stable mergesort. Stable
means that ties are broken to preserve the original order of appearance in the input
array. So

sort { ($a % 2) <=> ($b % 2) } (3,1,4,1,5,9);

will yield (4,3,1,1,5,9), guaranteed. The even and odd numbers appear in the output
in the same order they appeared in the input. Mergesort has worst case O(N log N)
behaviour, the best value attainable. And, ironically, this mergesort does
particularly well where quicksort goes quadratic: mergesort sorts (1..$N, 1..$N) in
O(N) time. But quicksort was rescued at the last moment because it is faster than
mergesort on certain inputs and platforms. For example, if you really don't care
about the order of even and odd digits, quicksort will run in O(N) time; it's very
good at sorting many repetitions of a small number of distinct elements. The
quicksort divide and conquer strategy works well on platforms with relatively small,
very fast, caches. Eventually, the problem gets whittled down to one that fits in the
cache, from which point it benefits from the increased memory speed.

Quicksort was rescued by implementing a sort pragma to control aspects of the sort.
The stable subpragma forces stable behaviour, regardless of algorithm. The _quicksort
and _mergesort subpragmas are heavy-handed ways to select the underlying
implementation. The leading "_" is a reminder that these subpragmas may not survive
beyond 5.8. More appropriate mechanisms for selecting the implementation exist, but
they wouldn't have arrived in time to save quicksort.

• Hashes now use Bob Jenkins "One-at-a-Time" hashing key algorithm (
http://burtleburtle.net/bob/hash/doobs.html ). This algorithm is reasonably fast
while producing a much better spread of values than the old hashing algorithm
(originally by Chris Torek, later tweaked by Ilya Zakharevich). Hash values output
from the algorithm on a hash of all 3-char printable ASCII keys comes much closer to
passing the DIEHARD random number generation tests. According to perlbench, this
change has not affected the overall speed of Perl.

• unshift() should now be noticeably faster.

Installation and Configuration Improvements

Generic Improvements
• INSTALL now explains how you can configure Perl to use 64-bit integers even on
non-64-bit platforms.

• Policy.sh policy change: if you are reusing a Policy.sh file (see INSTALL) and you use
Configure -Dprefix=/foo/bar and in the old Policy $prefix eq $siteprefix and $prefix
eq $vendorprefix, all of them will now be changed to the new prefix, /foo/bar.
(Previously only $prefix changed.) If you do not like this new behaviour, specify
prefix, siteprefix, and vendorprefix explicitly.

• A new optional location for Perl libraries, otherlibdirs, is available. It can be
used for example for vendor add-ons without disturbing Perl's own library directories.

• In many platforms, the vendor-supplied 'cc' is too stripped-down to build Perl
(basically, 'cc' doesn't do ANSI C). If this seems to be the case and 'cc' does not
seem to be the GNU C compiler 'gcc', an automatic attempt is made to find and use
'gcc' instead.

• gcc needs to closely track the operating system release to avoid build problems. If
Configure finds that gcc was built for a different operating system release than is
running, it now gives a clearly visible warning that there may be trouble ahead.

• Since Perl 5.8 is not binary-compatible with previous releases of Perl, Configure no
longer suggests including the 5.005 modules in @INC.

• Configure "-S" can now run non-interactively. [561]

• Configure support for pdp11-style memory models has been removed due to obsolescence.
[561]

• configure.gnu now works with options with whitespace in them.

• installperl now outputs everything to STDERR.

• Because PerlIO is now the default on most platforms, "-perlio" doesn't get appended to
the $Config{archname} (also known as $^O) anymore. Instead, if you explicitly choose
not to use perlio (Configure command line option -Uuseperlio), you will get "-stdio"
appended.

• Another change related to the architecture name is that "-64all" (-Duse64bitall, or
"maximally 64-bit") is appended only if your pointers are 64 bits wide. (To be exact,
the use64bitall is ignored.)

• In AFS installations, one can configure the root of the AFS to be somewhere else than
the default /afs by using the Configure parameter "-Dafsroot=/some/where/else".

• APPLLIB_EXP, a lesser-known configuration-time definition, has been documented. It
can be used to prepend site-specific directories to Perl's default search path (@INC);
see INSTALL for information.

• The version of Berkeley DB used when the Perl (and, presumably, the DB_File extension)
was built is now available as @Config{qw(db_version_major db_version_minor
db_version_patch)} from Perl and as "DB_VERSION_MAJOR_CFG DB_VERSION_MINOR_CFG
DB_VERSION_PATCH_CFG" from C.

• Building Berkeley DB3 for compatibility modes for DB, NDBM, and ODBM has been
documented in INSTALL.

• If you have CPAN access (either network or a local copy such as a CD-ROM) you can
during specify extra modules to Configure to build and install with Perl using the
-Dextras=... option. See INSTALL for more details.

• In addition to config.over, a new override file, config.arch, is available. This file
is supposed to be used by hints file writers for architecture-wide changes (as opposed
to config.over which is for site-wide changes).

• If your file system supports symbolic links, you can build Perl outside of the source
directory by

mkdir perl/build/directory
cd perl/build/directory
sh /path/to/perl/source/Configure -Dmksymlinks ...

This will create in perl/build/directory a tree of symbolic links pointing to files in
/path/to/perl/source. The original files are left unaffected. After Configure has
finished, you can just say

make all test

and Perl will be built and tested, all in perl/build/directory. [561]

• For Perl developers, several new make targets for profiling and debugging have been
added; see perlhack.

• Use of the gprof tool to profile Perl has been documented in perlhack. There
is a make target called "perl.gprof" for generating a gprofiled Perl
executable.

• If you have GCC 3, there is a make target called "perl.gcov" for creating a
gcoved Perl executable for coverage analysis. See perlhack.

• If you are on IRIX or Tru64 platforms, new profiling/debugging options have
been added; see perlhack for more information about pixie and Third Degree.

• Guidelines of how to construct minimal Perl installations have been added to INSTALL.

• The Thread extension is now not built at all under ithreads ("Configure
-Duseithreads") because it wouldn't work anyway (the Thread extension requires being
Configured with "-Duse5005threads").

Note that the 5.005 threads are unsupported and deprecated: if you have code written
for the old threads you should migrate it to the new ithreads model.

• The Gconvert macro ($Config{d_Gconvert}) used by perl for stringifying floating-point
numbers is now more picky about using sprintf %.*g rules for the conversion. Some
platforms that used to use gcvt may now resort to the slower sprintf.

• The obsolete method of making a special (e.g., debugging) flavor of perl by saying

make LIBPERL=libperld.a

has been removed. Use -DDEBUGGING instead.

New Or Improved Platforms
For the list of platforms known to support Perl, see "Supported Platforms" in perlport.

• AIX dynamic loading should be now better supported.

• AIX should now work better with gcc, threads, and 64-bitness. Also the long doubles
support in AIX should be better now. See perlaix.

• AtheOS ( http://www.atheos.cx/ ) is a new platform.

• BeOS has been reclaimed.

• The DG/UX platform now supports 5.005-style threads. See perldgux.

• The DYNIX/ptx platform (also known as dynixptx) is supported at or near osvers 4.5.2.

• EBCDIC platforms (z/OS (also known as OS/390), POSIX-BC, and VM/ESA) have been
regained. Many test suite tests still fail and the co-existence of Unicode and EBCDIC
isn't quite settled, but the situation is much better than with Perl 5.6. See
perlos390, perlbs2000 (for POSIX-BC), and perlvmesa for more information. (Note:
support for VM/ESA was removed in Perl v5.18.0. The relevant information was in
README.vmesa)

• Building perl with -Duseithreads or -Duse5005threads now works under HP-UX 10.20
(previously it only worked under 10.30 or later). You will need a thread library
package installed. See README.hpux. [561]

• Mac OS Classic is now supported in the mainstream source package (MacPerl has of
course been available since perl 5.004 but now the source code bases of standard Perl
and MacPerl have been synchronised) [561]

• Mac OS X (or Darwin) should now be able to build Perl even on HFS+ filesystems. (The
case-insensitivity used to confuse the Perl build process.)

• NCR MP-RAS is now supported. [561]

• All the NetBSD specific patches (except for the installation specific ones) have been
merged back to the main distribution.

• NetWare from Novell is now supported. See perlnetware.

• NonStop-UX is now supported. [561]

• NEC SUPER-UX is now supported.

• All the OpenBSD specific patches (except for the installation specific ones) have been
merged back to the main distribution.

• Perl has been tested with the GNU pth userlevel thread package (
http://www.gnu.org/software/pth/pth.html ). All thread tests of Perl now work, but
not without adding some yield()s to the tests, so while pth (and other userlevel
thread implementations) can be considered to be "working" with Perl ithreads, keep in
mind the possible non-preemptability of the underlying thread implementation.

• Stratus VOS is now supported using Perl's native build method (Configure). This is
the recommended method to build Perl on VOS. The older methods, which build miniperl,
are still available. See perlvos. [561+]

• The Amdahl UTS Unix mainframe platform is now supported. [561]

• WinCE is now supported. See perlce.

• z/OS (formerly known as OS/390, formerly known as MVS OE) now has support for dynamic
loading. This is not selected by default, however, you must specify -Dusedl in the
arguments of Configure. [561]

Selected Bug Fixes

       Numerous memory leaks and uninitialized memory accesses have been hunted down.  Most
       importantly, anonymous subs used to leak quite a bit. [561]

       •   The autouse pragma didn't work for Multi::Part::Function::Names.

       •   caller() could cause core dumps in certain situations.  Carp was sometimes affected by
           this problem.  In particular, caller() now returns a subroutine name of "(unknown)"
           for subroutines that have been removed from the symbol table.

       •   chop(@list) in list context returned the characters chopped in reverse order.  This
           has been reversed to be in the right order. [561]

       •   Configure no longer includes the DBM libraries (dbm, gdbm, db, ndbm) when building the
           Perl binary.  The only exception to this is SunOS 4.x, which needs them. [561]

       •   The behaviour of non-decimal but numeric string constants such as "0x23" was platform-
           dependent: in some platforms that was seen as 35, in some as 0, in some as a floating
           point number (don't ask).  This was caused by Perl's using the operating system
           libraries in a situation where the result of the string to number conversion is
           undefined: now Perl consistently handles such strings as zero in numeric contexts.

       •   Several debugger fixes: exit code now reflects the script exit code, condition "0" now
           treated correctly, the "d" command now checks line number, $. no longer gets
           corrupted, and all debugger output now goes correctly to the socket if RemotePort is
           set. [561]

       •   The debugger (perl5db.pl) has been modified to present a more consistent commands
           interface, via (CommandSet=580).  perl5db.t was also added to test the changes, and as
           a placeholder for further tests.

           See perldebug.

       •   The debugger has a new "dumpDepth" option to control the maximum depth to which nested
           structures are dumped.  The "x" command has been extended so that "x N EXPR" dumps out
           the value of EXPR to a depth of at most N levels.

       •   The debugger can now show lexical variables if you have the CPAN module PadWalker
           installed.

       •   The order of DESTROYs has been made more predictable.

       •   Perl 5.6.0 could emit spurious warnings about redefinition of dl_error() when
           statically building extensions into perl.  This has been corrected. [561]

       •   dprofpp -R didn't work.

       •   *foo{FORMAT} now works.

       •   Infinity is now recognized as a number.

       •   UNIVERSAL::isa no longer caches methods incorrectly.  (This broke the Tk extension
           with 5.6.0.) [561]

       •   Lexicals I: lexicals outside an eval "" weren't resolved correctly inside a subroutine
           definition inside the eval "" if they were not already referenced in the top level of
           the eval""ed code.

       •   Lexicals II: lexicals leaked at file scope into subroutines that were declared before
           the lexicals.

       •   Lexical warnings now propagating correctly between scopes and into "eval "..."".

       •   "use warnings qw(FATAL all)" did not work as intended.  This has been corrected. [561]

       •   warnings::enabled() now reports the state of $^W correctly if the caller isn't using
           lexical warnings. [561]

       •   Line renumbering with eval and "#line" now works. [561]

       •   Fixed numerous memory leaks, especially in eval "".

       •   Localised tied variables no longer leak memory

               use Tie::Hash;
               tie my %tied_hash => 'Tie::StdHash';

               ...

               # Used to leak memory every time local() was called;
               # in a loop, this added up.
               local($tied_hash{Foo}) = 1;

       •   Localised hash elements (and %ENV) are correctly unlocalised to not exist, if they
           didn't before they were localised.

               use Tie::Hash;
               tie my %tied_hash => 'Tie::StdHash';

               ...

               # Nothing has set the FOO element so far

               { local $tied_hash{FOO} = 'Bar' }

               # This used to print, but not now.
               print "exists!\n" if exists $tied_hash{FOO};

           As a side effect of this fix, tied hash interfaces must define the EXISTS and DELETE
           methods.

       •   mkdir() now ignores trailing slashes in the directory name, as mandated by POSIX.

       •   Some versions of glibc have a broken modfl().  This affects builds with
           "-Duselongdouble".  This version of Perl detects this brokenness and has a workaround
           for it.  The glibc release 2.2.2 is known to have fixed the modfl() bug.

       •   Modulus of unsigned numbers now works (4063328477 % 65535 used to return 27406,
           instead of 27047). [561]

       •   Some "not a number" warnings introduced in 5.6.0 eliminated to be more compatible with
           5.005.  Infinity is now recognised as a number. [561]

       •   Numeric conversions did not recognize changes in the string value properly in certain
           circumstances. [561]

       •   Attributes (such as :shared) didn't work with our().

       •   our() variables will not cause bogus "Variable will not stay shared" warnings. [561]

       •   "our" variables of the same name declared in two sibling blocks resulted in bogus
           warnings about "redeclaration" of the variables.  The problem has been corrected.
           [561]

       •   pack "Z" now correctly terminates the string with "\0".

       •   Fix password routines which in some shadow password platforms (e.g. HP-UX) caused
           getpwent() to return every other entry.

       •   The PERL5OPT environment variable (for passing command line arguments to Perl) didn't
           work for more than a single group of options. [561]

       •   PERL5OPT with embedded spaces didn't work.

       •   printf() no longer resets the numeric locale to "C".

       •   "qw(a\\b)" now parses correctly as 'a\\b': that is, as three characters, not four.
           [561]

       •   pos() did not return the correct value within s///ge in earlier versions.  This is now
           handled correctly. [561]

       •   Printing quads (64-bit integers) with printf/sprintf now works without the q L ll
           prefixes (assuming you are on a quad-capable platform).

       •   Regular expressions on references and overloaded scalars now work. [561+]

       •   Right-hand side magic (GMAGIC) could in many cases such as string concatenation be
           invoked too many times.

       •   scalar() now forces scalar context even when used in void context.

       •   SOCKS support is now much more robust.

       •   sort() arguments are now compiled in the right wantarray context (they were
           accidentally using the context of the sort() itself).  The comparison block is now run
           in scalar context, and the arguments to be sorted are always provided list context.
           [561]

       •   Changed the POSIX character class "[[:space:]]" to include the (very rarely used)
           vertical tab character.  Added a new POSIX-ish character class "[[:blank:]]" which
           stands for horizontal whitespace (currently, the space and the tab).

       •   The tainting behaviour of sprintf() has been rationalized.  It does not taint the
           result of floating point formats anymore, making the behaviour consistent with that of
           string interpolation. [561]

       •   Some cases of inconsistent taint propagation (such as within hash values) have been
           fixed.

       •   The RE engine found in Perl 5.6.0 accidentally pessimised certain kinds of simple
           pattern matches.  These are now handled better. [561]

       •   Regular expression debug output (whether through "use re 'debug'" or via "-Dr") now
           looks better. [561]

       •   Multi-line matches like ""a\nxb\n" =~ /(?!\A)x/m" were flawed.  The bug has been
           fixed. [561]

       •   Use of $& could trigger a core dump under some situations.  This is now avoided. [561]

       •   The regular expression captured submatches ($1, $2, ...) are now more consistently
           unset if the match fails, instead of leaving false data lying around in them. [561]

       •   readline() on files opened in "slurp" mode could return an extra "" (blank line) at
           the end in certain situations.  This has been corrected. [561]

       •   Autovivification of symbolic references of special variables described in perlvar (as
           in "${$num}") was accidentally disabled.  This works again now. [561]

       •   Sys::Syslog ignored the "LOG_AUTH" constant.

       •   $AUTOLOAD, sort(), lock(), and spawning subprocesses in multiple threads
           simultaneously are now thread-safe.

       •   Tie::Array's SPLICE method was broken.

       •   Allow a read-only string on the left-hand side of a non-modifying tr///.

       •   If "STDERR" is tied, warnings caused by "warn" and "die" now correctly pass to it.

       •   Several Unicode fixes.

           •       BOMs (byte order marks) at the beginning of Perl files (scripts, modules)
                   should now be transparently skipped.  UTF-16 and UCS-2 encoded Perl files
                   should now be read correctly.

           •       The character tables have been updated to Unicode 3.2.0.

           •       Comparing with utf8 data does not magically upgrade non-utf8 data into utf8.
                   (This was a problem for example if you were mixing data from I/O and Unicode
                   data: your output might have got magically encoded as UTF-8.)

           •       Generating illegal Unicode code points such as U+FFFE, or the UTF-16
                   surrogates, now also generates an optional warning.

           •       "IsAlnum", "IsAlpha", and "IsWord" now match titlecase.

           •       Concatenation with the "." operator or via variable interpolation, "eq",
                   "substr", "reverse", "quotemeta", the "x" operator, substitution with "s///",
                   single-quoted UTF-8, should now work.

           •       The "tr///" operator now works.  Note that the "tr///CU" functionality has
                   been removed (but see pack('U0', ...)).

           •       "eval "v200"" now works.

           •       Perl 5.6.0 parsed m/\x{ab}/ incorrectly, leading to spurious warnings.  This
                   has been corrected. [561]

           •       Zero entries were missing from the Unicode classes such as "IsDigit".

       •   Large unsigned numbers (those above 2**31) could sometimes lose their unsignedness,
           causing bogus results in arithmetic operations. [561]

       •   The Perl parser has been stress tested using both random input and Markov chain input
           and the few found crashes and lockups have been fixed.

   Platform Specific Changes and Fixes
       •   BSDI 4.*

           Perl now works on post-4.0 BSD/OSes.

       •   All BSDs

           Setting $0 now works (as much as possible; see perlvar for details).

       •   Cygwin

           Numerous updates; currently synchronised with Cygwin 1.3.10.

       •   Previously DYNIX/ptx had problems in its Configure probe for non-blocking I/O.

       •   EPOC

           EPOC now better supported.  See README.epoc. [561]

       •   FreeBSD 3.*

           Perl now works on post-3.0 FreeBSDs.

       •   HP-UX

           README.hpux updated; "Configure -Duse64bitall" now works; now uses HP-UX malloc
           instead of Perl malloc.

       •   IRIX

           Numerous compilation flag and hint enhancements; accidental mixing of 32-bit and
           64-bit libraries (a doomed attempt) made much harder.

       •   Linux

           •       Long doubles should now work (see INSTALL). [561]

           •       Linux previously had problems related to sockaddrlen when using accept(),
                   recvfrom() (in Perl: recv()), getpeername(), and getsockname().

       •   Mac OS Classic

           Compilation of the standard Perl distribution in Mac OS Classic should now work if you
           have the Metrowerks development environment and the missing Mac-specific toolkit bits.
           Contact the macperl mailing list for details.

       •   MPE/iX

           MPE/iX update after Perl 5.6.0.  See README.mpeix. [561]

       •   NetBSD/threads: try installing the GNU pth (should be in the packages collection, or
           http://www.gnu.org/software/pth/), and Configure with -Duseithreads.

       •   NetBSD/sparc

           Perl now works on NetBSD/sparc.

       •   OS/2

           Now works with usethreads (see INSTALL). [561]

       •   Solaris

           64-bitness using the Sun Workshop compiler now works.

       •   Stratus VOS

           The native build method requires at least VOS Release 14.5.0 and GNU C++/GNU Tools
           2.0.1 or later.  The Perl pack function now maps overflowed values to +infinity and
           underflowed values to -infinity.

       •   Tru64 (aka Digital UNIX, aka DEC OSF/1)

           The operating system version letter now recorded in $Config{osvers}.  Allow compiling
           with gcc (previously explicitly forbidden).  Compiling with gcc still not recommended
           because buggy code results, even with gcc 2.95.2.

       •   Unicos

           Fixed various alignment problems that lead into core dumps either during build or
           later; no longer dies on math errors at runtime; now using full quad integers (64
           bits), previously was using only 46 bit integers for speed.

       •   VMS

           See "Socket Extension Dynamic in VMS" and "IEEE-format Floating Point Default on
           OpenVMS Alpha" for important changes not otherwise listed here.

           chdir() now works better despite a CRT bug; now works with MULTIPLICITY (see INSTALL);
           now works with Perl's malloc.

           The tainting of %ENV elements via "keys" or "values" was previously unimplemented.  It
           now works as documented.

           The "waitpid" emulation has been improved.  The worst bug (now fixed) was that a pid
           of -1 would cause a wildcard search of all processes on the system.

           POSIX-style signals are now emulated much better on VMS versions prior to 7.0.

           The "system" function and backticks operator have improved functionality and better
           error handling. [561]

           File access tests now use current process privileges rather than the user's default
           privileges, which could sometimes result in a mismatch between reported access and
           actual access.  This improvement is only available on VMS v6.0 and later.

           There is a new "kill" implementation based on "sys$sigprc" that allows older VMS
           systems (pre-7.0) to use "kill" to send signals rather than simply force exit.  This
           implementation also allows later systems to call "kill" from within a signal handler.

           Iterative logical name translations are now limited to 10 iterations in imitation of
           SHOW LOGICAL and other OpenVMS facilities.

       •   Windows

           •       Signal handling now works better than it used to.  It is now implemented using
                   a Windows message loop, and is therefore less prone to random crashes.

           •       fork() emulation is now more robust, but still continues to have a few
                   esoteric bugs and caveats.  See perlfork for details. [561+]

           •       A failed (pseudo)fork now returns undef and sets errno to EAGAIN. [561]

           •       The following modules now work on Windows:

                       ExtUtils::Embed         [561]
                       IO::Pipe
                       IO::Poll
                       Net::Ping

           •       IO::File::new_tmpfile() is no longer limited to 32767 invocations per-process.

           •       Better chdir() return value for a non-existent directory.

           •       Compiling perl using the 64-bit Platform SDK tools is now supported.

           •       The Win32::SetChildShowWindow() builtin can be used to control the visibility
                   of windows created by child processes.  See Win32 for details.

           •       Non-blocking waits for child processes (or pseudo-processes) are supported via
                   "waitpid($pid, &POSIX::WNOHANG)".

           •       The behavior of system() with multiple arguments has been rationalized.  Each
                   unquoted argument will be automatically quoted to protect whitespace, and any
                   existing whitespace in the arguments will be preserved.  This improves the
                   portability of system(@args) by avoiding the need for Windows "cmd" shell
                   specific quoting in perl programs.

                   Note that this means that some scripts that may have relied on earlier buggy
                   behavior may no longer work correctly.  For example, "system("nmake /nologo",
                   @args)" will now attempt to run the file "nmake /nologo" and will fail when
                   such a file isn't found.  On the other hand, perl will now execute code such
                   as "system("c:/Program Files/MyApp/foo.exe", @args)" correctly.

           •       The perl header files no longer suppress common warnings from the Microsoft
                   Visual C++ compiler.  This means that additional warnings may now show up when
                   compiling XS code.

           •       Borland C++ v5.5 is now a supported compiler that can build Perl.  However,
                   the generated binaries continue to be incompatible with those generated by the
                   other supported compilers (GCC and Visual C++). [561]

           •       Duping socket handles with open(F, ">&MYSOCK") now works under Windows 9x.
                   [561]

           •       Current directory entries in %ENV are now correctly propagated to child
                   processes. [561]

           •       New %ENV entries now propagate to subprocesses. [561]

           •       Win32::GetCwd() correctly returns C:\ instead of C: when at the drive root.
                   Other bugs in chdir() and Cwd::cwd() have also been fixed. [561]

           •       The makefiles now default to the features enabled in ActiveState ActivePerl (a
                   popular Win32 binary distribution). [561]

           •       HTML files will now be installed in c:\perl\html instead of
                   c:\perl\lib\pod\html

           •       REG_EXPAND_SZ keys are now allowed in registry settings used by perl. [561]

           •       Can now send() from all threads, not just the first one. [561]

           •       ExtUtils::MakeMaker now uses $ENV{LIB} to search for libraries. [561]

           •       Less stack reserved per thread so that more threads can run concurrently.
                   (Still 16M per thread.) [561]

           •       "File::Spec->tmpdir()" now prefers C:/temp over /tmp (works better when perl
                   is running as service).

           •       Better UNC path handling under ithreads. [561]

           •       wait(), waitpid(), and backticks now return the correct exit status under
                   Windows 9x. [561]

           •       A socket handle leak in accept() has been fixed. [561]

New or Changed Diagnostics

Please see perldiag for more details.

• Ambiguous range in the transliteration operator (like a-z-9) now gives a warning.

• chdir("") and chdir(undef) now give a deprecation warning because they cause a
possible unintentional chdir to the home directory. Say chdir() if you really mean
that.

• Two new debugging options have been added: if you have compiled your Perl with
debugging, you can use the -DT [561] and -DR options to trace tokenising and to add
reference counts to displaying variables, respectively.

• The lexical warnings category "deprecated" is no longer a sub-category of the "syntax"
category. It is now a top-level category in its own right.

• Unadorned dump() will now give a warning suggesting to use explicit CORE::dump() if
that's what really is meant.

• The "Unrecognized escape" warning has been extended to include "\8", "\9", and "\_".
There is no need to escape any of the "\w" characters.

• All regular expression compilation error messages are now hopefully easier to
understand both because the error message now comes before the failed regex and
because the point of failure is now clearly marked by a "<-- HERE" marker.

• Various I/O (and socket) functions like binmode(), close(), and so forth now more
consistently warn if they are used illogically either on a yet unopened or on an
already closed filehandle (or socket).

• Using lstat() on a filehandle now gives a warning. (It's a non-sensical thing to do.)

• The "-M" and "-m" options now warn if you didn't supply the module name.

• If you in "use" specify a required minimum version, modules matching the name and but
not defining a $VERSION will cause a fatal failure.

• Using negative offset for vec() in lvalue context is now a warnable offense.

• Odd number of arguments to overload::constant now elicits a warning.

• Odd number of elements in anonymous hash now elicits a warning.

• The various "opened only for", "on closed", "never opened" warnings drop the "main::"
prefix for filehandles in the "main" package, for example "STDIN" instead of
"main::STDIN".

• Subroutine prototypes are now checked more carefully, you may get warnings for example
if you have used non-prototype characters.

• If an attempt to use a (non-blessed) reference as an array index is made, a warning is
given.

• "push @a;" and "unshift @a;" (with no values to push or unshift) now give a warning.
This may be a problem for generated and eval'ed code.

• If you try to "pack" in perlfunc a number less than 0 or larger than 255 using the "C"
format you will get an optional warning. Similarly for the "c" format and a number
less than -128 or more than 127.

• pack "P" format now demands an explicit size.

• unpack "w" now warns of unterminated compressed integers.

• Warnings relating to the use of PerlIO have been added.

• Certain regex modifiers such as "(?o)" make sense only if applied to the entire regex.
You will get an optional warning if you try to do otherwise.

• Variable length lookbehind has not yet been implemented, trying to use it will tell
that.

• Using arrays or hashes as references (e.g. "%foo->{bar}" has been deprecated for a
while. Now you will get an optional warning.

• Warnings relating to the use of the new restricted hashes feature have been added.

• Self-ties of arrays and hashes are not supported and fatal errors will happen even at
an attempt to do so.

• Using "sort" in scalar context now issues an optional warning. This didn't do
anything useful, as the sort was not performed.

• Using the /g modifier in split() is meaningless and will cause a warning.

• Using splice() past the end of an array now causes a warning.

• Malformed Unicode encodings (UTF-8 and UTF-16) cause a lot of warnings, as does trying
to use UTF-16 surrogates (which are unimplemented).

• Trying to use Unicode characters on an I/O stream without marking the stream's
encoding (using open() or binmode()) will cause "Wide character" warnings.

• Use of v-strings in use/require causes a (backward) portability warning.

• Warnings relating to the use interpreter threads and their shared data have been
added.

Changed Internals

• PerlIO is now the default.

• perlapi.pod (a companion to perlguts) now attempts to document the internal API.

• You can now build a really minimal perl called microperl. Building microperl does not
require even running Configure; "make -f Makefile.micro" should be enough. Beware:
microperl makes many assumptions, some of which may be too bold; the resulting
executable may crash or otherwise misbehave in wondrous ways. For careful hackers
only.

• Added rsignal(), whichsig(), do_join(), op_clear, op_null, ptr_table_clear(),
ptr_table_free(), sv_setref_uv(), and several UTF-8 interfaces to the publicised API.
For the full list of the available APIs see perlapi.

• Made possible to propagate customised exceptions via croak()ing.

• Now xsubs can have attributes just like subs. (Well, at least the built-in
attributes.)

• dTHR and djSP have been obsoleted; the former removed (because it's a no-op) and the
latter replaced with dSP.

• PERL_OBJECT has been completely removed.

• The MAGIC constants (e.g. 'P') have been macrofied (e.g. "PERL_MAGIC_TIED") for better
source code readability and maintainability.

• The regex compiler now maintains a structure that identifies nodes in the compiled
bytecode with the corresponding syntactic features of the original regex expression.
The information is attached to the new "offsets" member of the "struct regexp". See
perldebguts for more complete information.

• The C code has been made much more "gcc -Wall" clean. Some warning messages still
remain in some platforms, so if you are compiling with gcc you may see some warnings
about dubious practices. The warnings are being worked on.

• perly.c, sv.c, and sv.h have now been extensively commented.

• Documentation on how to use the Perl source repository has been added to
Porting/repository.pod.

• There are now several profiling make targets.

Security Vulnerability Closed [561]

(This change was already made in 5.7.0 but bears repeating here.) (5.7.0 came out before
5.6.1: the development branch 5.7 released earlier than the maintenance branch 5.6)

A potential security vulnerability in the optional suidperl component of Perl was
identified in August 2000. suidperl is neither built nor installed by default. As of
November 2001 the only known vulnerable platform is Linux, most likely all Linux
distributions. CERT and various vendors and distributors have been alerted about the
vulnerability. See http://www.cpan.org/src/5.0/sperl-2000-08-05/sperl-2000-08-05.txt for
more information.

The problem was caused by Perl trying to report a suspected security exploit attempt using
an external program, /bin/mail. On Linux platforms the /bin/mail program had an
undocumented feature which when combined with suidperl gave access to a root shell,
resulting in a serious compromise instead of reporting the exploit attempt. If you don't
have /bin/mail, or if you have 'safe setuid scripts', or if suidperl is not installed, you
are safe.

The exploit attempt reporting feature has been completely removed from Perl 5.8.0 (and the
maintenance release 5.6.1, and it was removed also from all the Perl 5.7 releases), so
that particular vulnerability isn't there anymore. However, further security
vulnerabilities are, unfortunately, always possible. The suidperl functionality is most
probably going to be removed in Perl 5.10. In any case, suidperl should only be used by
security experts who know exactly what they are doing and why they are using suidperl
instead of some other solution such as sudo ( see http://www.courtesan.com/sudo/ ).

New Tests

       Several new tests have been added, especially for the lib and ext subsections.  There are
       now about 69 000 individual tests (spread over about 700 test scripts), in the regression
       suite (5.6.1 has about 11 700 tests, in 258 test scripts)  The exact numbers depend on the
       platform and Perl configuration used.  Many of the new tests are of course introduced by
       the new modules, but still in general Perl is now more thoroughly tested.

       Because of the large number of tests, running the regression suite will take considerably
       longer time than it used to: expect the suite to take up to 4-5 times longer to run than
       in perl 5.6.  On a really fast machine you can hope to finish the suite in about 6-8
       minutes (wallclock time).

       The tests are now reported in a different order than in earlier Perls.  (This happens
       because the test scripts from under t/lib have been moved to be closer to the
       library/extension they are testing.)

Known Problems

The Compiler Suite Is Still Very Experimental
The compiler suite is slowly getting better but it continues to be highly experimental.
Use in production environments is discouraged.

Localising Tied Arrays and Hashes Is Broken
local %tied_array;

doesn't work as one would expect: the old value is restored incorrectly. This will be
changed in a future release, but we don't know yet what the new semantics will exactly be.
In any case, the change will break existing code that relies on the current (ill-defined)
semantics, so just avoid doing this in general.

Building Extensions Can Fail Because Of Largefiles
Some extensions like mod_perl are known to have issues with `largefiles', a change brought
by Perl 5.6.0 in which file offsets default to 64 bits wide, where supported. Modules may
fail to compile at all, or they may compile and work incorrectly. Currently, there is no
good solution for the problem, but Configure now provides appropriate non-largefile
ccflags, ldflags, libswanted, and libs in the %Config hash (e.g.,
$Config{ccflags_nolargefiles}) so the extensions that are having problems can try
configuring themselves without the largefileness. This is admittedly not a clean
solution, and the solution may not even work at all. One potential failure is whether one
can (or, if one can, whether it's a good idea to) link together at all binaries with
different ideas about file offsets; all this is platform-dependent.

Modifying $_ Inside for(..)
for (1..5) { $_++ }

works without complaint. It shouldn't. (You should be able to modify only lvalue
elements inside the loops.) You can see the correct behaviour by replacing the 1..5 with
1, 2, 3, 4, 5.

mod_perl 1.26 Doesn't Build With Threaded Perl
Use mod_perl 1.27 or higher.

lib/ftmp-security tests warn 'system possibly insecure'
Don't panic. Read the 'make test' section of INSTALL instead.

libwww-perl (LWP) fails base/date #51
Use libwww-perl 5.65 or later.

PDL failing some tests
Use PDL 2.3.4 or later.

Perl_get_sv
You may get errors like 'Undefined symbol "Perl_get_sv"' or "can't resolve symbol
'Perl_get_sv'", or the symbol may be "Perl_sv_2pv". This probably means that you are
trying to use an older shared Perl library (or extensions linked with such) with Perl
5.8.0 executable. Perl used to have such a subroutine, but that is no more the case.
Check your shared library path, and any shared Perl libraries in those directories.

Sometimes this problem may also indicate a partial Perl 5.8.0 installation, see "Mac OS X
dyld undefined symbols" for an example and how to deal with it.

Self-tying Problems
Self-tying of arrays and hashes is broken in rather deep and hard-to-fix ways. As a stop-
gap measure to avoid people from getting frustrated at the mysterious results (core dumps,
most often), it is forbidden for now (you will get a fatal error even from an attempt).

A change to self-tying of globs has caused them to be recursively referenced (see: "Two-
Phased Garbage Collection" in perlobj). You will now need an explicit untie to destroy a
self-tied glob. This behaviour may be fixed at a later date.

Self-tying of scalars and IO thingies works.

ext/threads/t/libc
If this test fails, it indicates that your libc (C library) is not threadsafe. This
particular test stress tests the localtime() call to find out whether it is threadsafe.
See perlthrtut for more information.

Failure of Thread (5.005-style) tests
Note that support for 5.005-style threading is deprecated, experimental and practically
unsupported. In 5.10, it is expected to be removed. You should migrate your code to
ithreads.

The following tests are known to fail due to fundamental problems in the 5.005 threading
implementation. These are not new failures--Perl 5.005_0x has the same bugs, but didn't
have these tests.

../ext/B/t/xref.t 255 65280 14 12 85.71% 3-14
../ext/List/Util/t/first.t 255 65280 7 4 57.14% 2 5-7
../lib/English.t 2 512 54 2 3.70% 2-3
../lib/FileCache.t 5 1 20.00% 5
../lib/Filter/Simple/t/data.t 6 3 50.00% 1-3
../lib/Filter/Simple/t/filter_only. 9 3 33.33% 1-2 5
../lib/Math/BigInt/t/bare_mbf.t 1627 4 0.25% 8 11 1626-1627
../lib/Math/BigInt/t/bigfltpm.t 1629 4 0.25% 10 13 1628-
1629
../lib/Math/BigInt/t/sub_mbf.t 1633 4 0.24% 8 11 1632-1633
../lib/Math/BigInt/t/with_sub.t 1628 4 0.25% 9 12 1627-1628
../lib/Tie/File/t/31_autodefer.t 255 65280 65 32 49.23% 34-65
../lib/autouse.t 10 1 10.00% 4
op/flip.t 15 1 6.67% 15

These failures are unlikely to get fixed as 5.005-style threads are considered
fundamentally broken. (Basically what happens is that competing threads can corrupt
shared global state, one good example being regular expression engine's state.)

Timing problems
The following tests may fail intermittently because of timing problems, for example if the
system is heavily loaded.

t/op/alarm.t
ext/Time/HiRes/HiRes.t
lib/Benchmark.t
lib/Memoize/t/expmod_t.t
lib/Memoize/t/speed.t

In case of failure please try running them manually, for example

./perl -Ilib ext/Time/HiRes/HiRes.t

Tied/Magical Array/Hash Elements Do Not Autovivify
For normal arrays "$foo = \$bar[1]" will assign "undef" to $bar[1] (assuming that it
didn't exist before), but for tied/magical arrays and hashes such autovivification does
not happen because there is currently no way to catch the reference creation. The same
problem affects slicing over non-existent indices/keys of a tied/magical array/hash.

Unicode in package/class and subroutine names does not work
One can have Unicode in identifier names, but not in package/class or subroutine names.
While some limited functionality towards this does exist as of Perl 5.8.0, that is more
accidental than designed; use of Unicode for the said purposes is unsupported.

One reason of this unfinishedness is its (currently) inherent unportability: since both
package names and subroutine names may need to be mapped to file and directory names, the
Unicode capability of the filesystem becomes important-- and there unfortunately aren't
portable answers.

Platform Specific Problems

   AIX
       •   If using the AIX native make command, instead of just "make" issue "make all".  In
           some setups the former has been known to spuriously also try to run "make install".
           Alternatively, you may want to use GNU make.

       •   In AIX 4.2, Perl extensions that use C++ functions that use statics may have problems
           in that the statics are not getting initialized.  In newer AIX releases, this has been
           solved by linking Perl with the libC_r library, but unfortunately in AIX 4.2 the said
           library has an obscure bug where the various functions related to time (such as time()
           and gettimeofday()) return broken values, and therefore in AIX 4.2 Perl is not linked
           against libC_r.

       •   vac 5.0.0.0 May Produce Buggy Code For Perl

           The AIX C compiler vac version 5.0.0.0 may produce buggy code, resulting in a few
           random tests failing when run as part of "make test", but when the failing tests are
           run by hand, they succeed.  We suggest upgrading to at least vac version 5.0.1.0, that
           has been known to compile Perl correctly.  "lslpp -L|grep vac.C" will tell you the vac
           version.  See README.aix.

       •   If building threaded Perl, you may get compilation warning from pp_sys.c:

             "pp_sys.c", line 4651.39: 1506-280 (W) Function argument assignment between types "unsigned char*" and "const void*" is not allowed.

           This is harmless; it is caused by the getnetbyaddr() and getnetbyaddr_r() having
           slightly different types for their first argument.

   Alpha systems with old gccs fail several tests
       If you see op/pack, op/pat, op/regexp, or ext/Storable tests failing in a Linux/alpha or
       *BSD/Alpha, it's probably time to upgrade your gcc.  gccs prior to 2.95.3 are definitely
       not good enough, and gcc 3.1 may be even better.  (RedHat Linux/alpha with gcc 3.1
       reported no problems, as did Linux 2.4.18 with gcc 2.95.4.)  (In Tru64, it is preferable
       to use the bundled C compiler.)

   AmigaOS
       Perl 5.8.0 doesn't build in AmigaOS.  It broke at some point during the ithreads work and
       we could not find Amiga experts to unbreak the problems.  Perl 5.6.1 still works for
       AmigaOS (as does the 5.7.2 development release).

   BeOS
       The following tests fail on 5.8.0 Perl in BeOS Personal 5.03:

        t/op/lfs............................FAILED at test 17
        t/op/magic..........................FAILED at test 24
        ext/Fcntl/t/syslfs..................FAILED at test 17
        ext/File/Glob/t/basic...............FAILED at test 3
        ext/POSIX/t/sigaction...............FAILED at test 13
        ext/POSIX/t/waitpid.................FAILED at test 1

       (Note: more information was available in README.beos until support for BeOS was removed in
       Perl v5.18.0)

   Cygwin "unable to remap"
       For example when building the Tk extension for Cygwin, you may get an error message saying
       "unable to remap".  This is known problem with Cygwin, and a workaround is detailed in
       here: http://sources.redhat.com/ml/cygwin/2001-12/msg00894.html

   Cygwin ndbm tests fail on FAT
       One can build but not install (or test the build of) the NDBM_File on FAT filesystems.
       Installation (or build) on NTFS works fine.  If one attempts the test on a FAT install (or
       build) the following failures are expected:

        ../ext/NDBM_File/ndbm.t       13  3328    71   59  83.10%  1-2 4 16-71
        ../ext/ODBM_File/odbm.t      255 65280    ??   ??       %  ??
        ../lib/AnyDBM_File.t           2   512    12    2  16.67%  1 4
        ../lib/Memoize/t/errors.t      0   139    11    5  45.45%  7-11
        ../lib/Memoize/t/tie_ndbm.t   13  3328     4    4 100.00%  1-4
        run/fresh_perl.t                          97    1   1.03%  91

       NDBM_File fails and ODBM_File just coredumps.

       If you intend to run only on FAT (or if using AnyDBM_File on FAT), run Configure with the
       -Ui_ndbm and -Ui_dbm options to prevent NDBM_File and ODBM_File being built.

   DJGPP Failures
        t/op/stat............................FAILED at test 29
        lib/File/Find/t/find.................FAILED at test 1
        lib/File/Find/t/taint................FAILED at test 1
        lib/h2xs.............................FAILED at test 15
        lib/Pod/t/eol........................FAILED at test 1
        lib/Test/Harness/t/strap-analyze.....FAILED at test 8
        lib/Test/Harness/t/test-harness......FAILED at test 23
        lib/Test/Simple/t/exit...............FAILED at test 1

       The above failures are known as of 5.8.0 with native builds with long filenames, but there
       are a few more if running under dosemu because of limitations (and maybe bugs) of dosemu:

        t/comp/cpp...........................FAILED at test 3
        t/op/inccode.........................(crash)

       and a few lib/ExtUtils tests, and several hundred Encode/t/Aliases.t failures that work
       fine with long filenames.  So you really might prefer native builds and long filenames.

   FreeBSD built with ithreads coredumps reading large directories
       This is a known bug in FreeBSD 4.5's readdir_r(), it has been fixed in FreeBSD 4.6 (see
       perlfreebsd (README.freebsd)).

   FreeBSD Failing locale Test 117 For ISO 8859-15 Locales
       The ISO 8859-15 locales may fail the locale test 117 in FreeBSD.  This is caused by the
       characters \xFF (y with diaeresis) and \xBE (Y with diaeresis) not behaving correctly when
       being matched case-insensitively.  Apparently this problem has been fixed in the latest
       FreeBSD releases.  ( http://www.freebsd.org/cgi/query-pr.cgi?pr=34308 )

   IRIX fails ext/List/Util/t/shuffle.t or Digest::MD5
       IRIX with MIPSpro 7.3.1.2m or 7.3.1.3m compiler may fail the List::Util test
       ext/List/Util/t/shuffle.t by dumping core.  This seems to be a compiler error since if
       compiled with gcc no core dump ensues, and no failures have been seen on the said test on
       any other platform.

       Similarly, building the Digest::MD5 extension has been known to fail with "*** Termination
       code 139 (bu21)".

       The cure is to drop optimization level (Configure -Doptimize=-O2).

   HP-UX lib/posix Subtest 9 Fails When LP64-Configured
       If perl is configured with -Duse64bitall, the successful result of the subtest 10 of
       lib/posix may arrive before the successful result of the subtest 9, which confuses the
       test harness so much that it thinks the subtest 9 failed.

   Linux with glibc 2.2.5 fails t/op/int subtest #6 with -Duse64bitint
       This is a known bug in the glibc 2.2.5 with long long integers.  (
       http://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=65612 )

   Linux With Sfio Fails op/misc Test 48
       No known fix.

   Mac OS X
       Please remember to set your environment variable LC_ALL to "C" (setenv LC_ALL C) before
       running "make test" to avoid a lot of warnings about the broken locales of Mac OS X.

       The following tests are known to fail in Mac OS X 10.1.5 because of buggy (old)
       implementations of Berkeley DB included in Mac OS X:

        Failed Test                 Stat Wstat Total Fail  Failed  List of Failed
        -------------------------------------------------------------------------
        ../ext/DB_File/t/db-btree.t    0    11    ??   ??       %  ??
        ../ext/DB_File/t/db-recno.t              149    3   2.01%  61 63 65

       If you are building on a UFS partition, you will also probably see t/op/stat.t subtest #9
       fail.  This is caused by Darwin's UFS not supporting inode change time.

       Also the ext/POSIX/t/posix.t subtest #10 fails but it is skipped for now because the
       failure is Apple's fault, not Perl's (blocked signals are lost).

       If you Configure with ithreads, ext/threads/t/libc.t will fail. Again, this is not Perl's
       fault-- the libc of Mac OS X is not threadsafe (in this particular test, the localtime()
       call is found to be threadunsafe.)

   Mac OS X dyld undefined symbols
       If after installing Perl 5.8.0 you are getting warnings about missing symbols, for example

           dyld: perl Undefined symbols
           _perl_sv_2pv
           _perl_get_sv

       you probably have an old pre-Perl-5.8.0 installation (or parts of one) in /Library/Perl
       (the undefined symbols used to exist in pre-5.8.0 Perls).  It seems that for some reason
       "make install" doesn't always completely overwrite the files in /Library/Perl.  You can
       move the old Perl shared library out of the way like this:

           cd /Library/Perl/darwin/CORE
           mv libperl.dylib libperlold.dylib

       and then reissue "make install".  Note that the above of course is extremely disruptive
       for anything using the /usr/local/bin/perl.  If that doesn't help, you may have to try
       removing all the .bundle files from beneath /Library/Perl, and again "make install"-ing.

   OS/2 Test Failures
       The following tests are known to fail on OS/2 (for clarity only the failures are shown,
       not the full error messages):

        ../lib/ExtUtils/t/Mkbootstrap.t    1   256    18    1   5.56%  8
        ../lib/ExtUtils/t/Packlist.t       1   256    34    1   2.94%  17
        ../lib/ExtUtils/t/basic.t          1   256    17    1   5.88%  14
        lib/os2_process.t                  2   512   227    2   0.88%  174 209
        lib/os2_process_kid.t                        227    2   0.88%  174 209
        lib/rx_cmprt.t                   255 65280    18    3  16.67%  16-18

   op/sprintf tests 91, 129, and 130
       The op/sprintf tests 91, 129, and 130 are known to fail on some platforms.  Examples
       include any platform using sfio, and Compaq/Tandem's NonStop-UX.

       Test 91 is known to fail on QNX6 (nto), because "sprintf '%e',0" incorrectly produces
       0.000000e+0 instead of 0.000000e+00.

       For tests 129 and 130, the failing platforms do not comply with the ANSI C Standard: lines
       19ff on page 134 of ANSI X3.159 1989, to be exact.  (They produce something other than "1"
       and "-1" when formatting 0.6 and -0.6 using the printf format "%.0f"; most often, they
       produce "0" and "-0".)

   SCO
       The socketpair tests are known to be unhappy in SCO 3.2v5.0.4:

        ext/Socket/socketpair.t...............FAILED tests 15-45

   Solaris 2.5
       In case you are still using Solaris 2.5 (aka SunOS 5.5), you may experience failures (the
       test core dumping) in lib/locale.t.  The suggested cure is to upgrade your Solaris.

   Solaris x86 Fails Tests With -Duse64bitint
       The following tests are known to fail in Solaris x86 with Perl configured to use 64 bit
       integers:

        ext/Data/Dumper/t/dumper.............FAILED at test 268
        ext/Devel/Peek/Peek..................FAILED at test 7

   SUPER-UX (NEC SX)
       The following tests are known to fail on SUPER-UX:

        op/64bitint...........................FAILED tests 29-30, 32-33, 35-36
        op/arith..............................FAILED tests 128-130
        op/pack...............................FAILED tests 25-5625
        op/pow................................
        op/taint..............................# msgsnd failed
        ../ext/IO/lib/IO/t/io_poll............FAILED tests 3-4
        ../ext/IPC/SysV/ipcsysv...............FAILED tests 2, 5-6
        ../ext/IPC/SysV/t/msg.................FAILED tests 2, 4-6
        ../ext/Socket/socketpair..............FAILED tests 12
        ../lib/IPC/SysV.......................FAILED tests 2, 5-6
        ../lib/warnings.......................FAILED tests 115-116, 118-119

       The op/pack failure ("Cannot compress negative numbers at op/pack.t line 126") is serious
       but as of yet unsolved.  It points at some problems with the signedness handling of the C
       compiler, as do the 64bitint, arith, and pow failures.  Most of the rest point at problems
       with SysV IPC.

   Term::ReadKey not working on Win32
       Use Term::ReadKey 2.20 or later.

   UNICOS/mk
       •   During Configure, the test

               Guessing which symbols your C compiler and preprocessor define...

           will probably fail with error messages like

               CC-20 cc: ERROR File = try.c, Line = 3
                 The identifier "bad" is undefined.

                 bad switch yylook 79bad switch yylook 79bad switch yylook 79bad switch yylook 79#ifdef A29K
                 ^

               CC-65 cc: ERROR File = try.c, Line = 3
                 A semicolon is expected at this point.

           This is caused by a bug in the awk utility of UNICOS/mk.  You can ignore the error,
           but it does cause a slight problem: you cannot fully benefit from the h2ph utility
           (see h2ph) that can be used to convert C headers to Perl libraries, mainly used to be
           able to access from Perl the constants defined using C preprocessor, cpp.  Because of
           the above error, parts of the converted headers will be invisible.  Luckily, these
           days the need for h2ph is rare.

       •   If building Perl with interpreter threads (ithreads), the getgrent(), getgrnam(), and
           getgrgid() functions cannot return the list of the group members due to a bug in the
           multithreaded support of UNICOS/mk.  What this means is that in list context the
           functions will return only three values, not four.

   UTS
       There are a few known test failures.  (Note: the relevant information was available in
       README.uts until support for UTS was removed in Perl v5.18.0)

   VOS (Stratus)
       When Perl is built using the native build process on VOS Release 14.5.0 and GNU C++/GNU
       Tools 2.0.1, all attempted tests either pass or result in TODO (ignored) failures.

   VMS
       There should be no reported test failures with a default configuration, though there are a
       number of tests marked TODO that point to areas needing further debugging and/or porting
       work.

   Win32
       In multi-CPU boxes, there are some problems with the I/O buffering: some output may appear
       twice.

   XML::Parser not working
       Use XML::Parser 2.31 or later.

   z/OS (OS/390)
       z/OS has rather many test failures but the situation is actually much better than it was
       in 5.6.0; it's just that so many new modules and tests have been added.

        Failed Test                   Stat Wstat Total Fail  Failed  List of Failed
        ---------------------------------------------------------------------------
        ../ext/Data/Dumper/t/dumper.t              357    8   2.24%  311 314 325 327
                                                                     331 333 337 339
        ../ext/IO/lib/IO/t/io_unix.t                 5    4  80.00%  2-5
        ../ext/Storable/t/downgrade.t   12  3072   169   12   7.10%  14-15 46-47 78-79
                                                                     110-111 150 161
        ../lib/ExtUtils/t/Constant.t   121 30976    48   48 100.00%  1-48
        ../lib/ExtUtils/t/Embed.t                    9    9 100.00%  1-9
        op/pat.t                                   922    7   0.76%  665 776 785 832-
                                                                     834 845
        op/sprintf.t                               224    3   1.34%  98 100 136
        op/tr.t                                     97    5   5.15%  63 71-74
        uni/fold.t                                 780    6   0.77%  61 169 196 661
                                                                     710-711

       The failures in dumper.t and downgrade.t are problems in the tests, those in io_unix and
       sprintf are problems in the USS (UDP sockets and printf formats).  The pat, tr, and fold
       failures are genuine Perl problems caused by EBCDIC (and in the pat and fold cases,
       combining that with Unicode).  The Constant and Embed are probably problems in the tests
       (since they test Perl's ability to build extensions, and that seems to be working
       reasonably well.)

   Unicode Support on EBCDIC Still Spotty
       Though mostly working, Unicode support still has problem spots on EBCDIC platforms.  One
       such known spot are the "\p{}" and "\P{}" regular expression constructs for code points
       less than 256: the "pP" are testing for Unicode code points, not knowing about EBCDIC.

   Seen In Perl 5.7 But Gone Now
       "Time::Piece" (previously known as "Time::Object") was removed because it was felt that it
       didn't have enough value in it to be a core module.  It is still a useful module, though,
       and is available from the CPAN.

       Perl 5.8 unfortunately does not build anymore on AmigaOS; this broke accidentally at some
       point.  Since there are not that many Amiga developers available, we could not get this
       fixed and tested in time for 5.8.0.  Perl 5.6.1 still works for AmigaOS (as does the 5.7.2
       development release).

       The "PerlIO::Scalar" and "PerlIO::Via" (capitalised) were renamed as "PerlIO::scalar" and
       "PerlIO::via" (all lowercase) just before 5.8.0.  The main rationale was to have all core
       PerlIO layers to have all lowercase names.  The "plugins" are named as usual, for example
       "PerlIO::via::QuotedPrint".

       The "threads::shared::queue" and "threads::shared::semaphore" were renamed as
       "Thread::Queue" and "Thread::Semaphore" just before 5.8.0.  The main rationale was to have
       thread modules to obey normal naming, "Thread::" (the "threads" and "threads::shared"
       themselves are more pragma-like, they affect compile-time, so they stay lowercase).

Reporting Bugs

       If you find what you think is a bug, you might check the articles recently posted to the
       comp.lang.perl.misc newsgroup and the perl bug database at http://bugs.perl.org/ .  There
       may also be information at http://www.perl.com/ , the Perl Home Page.

       If you believe you have an unreported bug, please run the perlbug program included with
       your release.  Be sure to trim your bug down to a tiny but sufficient test case.  Your bug
       report, along with the output of "perl -V", will be sent off to perlbug@perl.org to be
       analysed by the Perl porting team.

HISTORY

       Written by Jarkko Hietaniemi <jhi@iki.fi>.