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/unicode/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>.

perl v5.34.0                                       2025-04-08                                     PERL58DELTA(1)