man > perl581delta(1)

PERL581DELTA(1)                   Perl Programmers Reference Guide                   PERL581DELTA(1)



NAME
       perl581delta - what is new for perl v5.8.1

DESCRIPTION
       This document describes differences between the 5.8.0 release and the 5.8.1 release.

       If you are upgrading from an earlier release such as 5.6.1, first read the perl58delta, which
       describes differences between 5.6.0 and 5.8.0.

       In case you are wondering about 5.6.1, it was bug-fix-wise rather identical to the
       development release 5.7.1.  Confused?  This timeline hopefully helps a bit: it lists the new
       major releases, their maintenance releases, and the development releases.

                 New     Maintenance  Development

                 5.6.0                             2000-Mar-22
                                      5.7.0        2000-Sep-02
                         5.6.1                     2001-Apr-08
                                      5.7.1        2001-Apr-09
                                      5.7.2        2001-Jul-13
                                      5.7.3        2002-Mar-05
                 5.8.0                             2002-Jul-18
                         5.8.1                     2003-Sep-25

Incompatible Changes
   Hash Randomisation
       Mainly due to security reasons, the "random ordering" of hashes has been made even more
       random.  Previously while the order of hash elements from keys(), values(), and each() was
       essentially random, it was still repeatable.  Now, however, the order varies between
       different runs of Perl.

       Perl has never guaranteed any ordering of the hash keys, and the ordering has already changed
       several times during the lifetime of Perl 5.  Also, the ordering of hash keys has always
       been, and continues to be, affected by the insertion order.

       The added randomness may affect applications.

       One possible scenario is when output of an application has included hash data.  For example,
       if you have used the Data::Dumper module to dump data into different files, and then compared
       the files to see whether the data has changed, now you will have false positives since the
       order in which hashes are dumped will vary.  In general the cure is to sort the keys (or the
       values); in particular for Data::Dumper to use the "Sortkeys" option.  If some particular
       order is really important, use tied hashes: for example the Tie::IxHash module which by
       default preserves the order in which the hash elements were added.

       More subtle problem is reliance on the order of "global destruction".  That is what happens
       at the end of execution: Perl destroys all data structures, including user data.  If your
       destructors (the DESTROY subroutines) have assumed any particular ordering to the global
       destruction, there might be problems ahead.  For example, in a destructor of one object you
       cannot assume that objects of any other class are still available, unless you hold a
       reference to them.  If the environment variable PERL_DESTRUCT_LEVEL is set to a non-zero
       value, or if Perl is exiting a spawned thread, it will also destruct the ordinary references
       and the symbol tables that are no longer in use.  You can't call a class method or an
       ordinary function on a class that has been collected that way.

       The hash randomisation is certain to reveal hidden assumptions about some particular ordering
       of hash elements, and outright bugs: it revealed a few bugs in the Perl core and core
       modules.

       To disable the hash randomisation in runtime, set the environment variable PERL_HASH_SEED to
       0 (zero) before running Perl (for more information see "PERL_HASH_SEED" in perlrun), or to
       disable the feature completely in compile time, compile with "-DNO_HASH_SEED" (see INSTALL).

       See "Algorithmic Complexity Attacks" in perlsec for the original rationale behind this
       change.

   UTF-8 On Filehandles No Longer Activated By Locale
       In Perl 5.8.0 all filehandles, including the standard filehandles, were implicitly set to be
       in Unicode UTF-8 if the locale settings indicated the use of UTF-8.  This feature caused too
       many problems, so the feature was turned off and redesigned: see "Core Enhancements".

   Single-number v-strings are no longer v-strings before "=>"
       The version strings or v-strings (see "Version Strings" in perldata) feature introduced in
       Perl 5.6.0 has been a source of some confusion-- especially when the user did not want to use
       it, but Perl thought it knew better.  Especially troublesome has been the feature that before
       a "=>" a version string (a "v" followed by digits) has been interpreted as a v-string instead
       of a string literal.  In other words:

               %h = ( v65 => 42 );

       has meant since Perl 5.6.0

               %h = ( 'A' => 42 );

       (at least in platforms of ASCII progeny)  Perl 5.8.1 restores the more natural interpretation

               %h = ( 'v65' => 42 );

       The multi-number v-strings like v65.66 and 65.66.67 still continue to be v-strings in Perl
       5.8.

   (Win32) The -C Switch Has Been Repurposed
       The -C switch has changed in an incompatible way.  The old semantics of this switch only made
       sense in Win32 and only in the "use utf8" universe in 5.6.x releases, and do not make sense
       for the Unicode implementation in 5.8.0.  Since this switch could not have been used by
       anyone, it has been repurposed.  The behavior that this switch enabled in 5.6.x releases may
       be supported in a transparent, data-dependent fashion in a future release.

       For the new life of this switch, see "UTF-8 no longer default under UTF-8 locales", and "-C"
       in perlrun.

   (Win32) The /d Switch Of cmd.exe
       Perl 5.8.1 uses the /d switch when running the cmd.exe shell internally for system(),
       backticks, and when opening pipes to external programs.  The extra switch disables the
       execution of AutoRun commands from the registry, which is generally considered undesirable
       when running external programs.  If you wish to retain compatibility with the older behavior,
       set PERL5SHELL in your environment to "cmd /x/c".

Core Enhancements
   UTF-8 no longer default under UTF-8 locales
       In Perl 5.8.0 many Unicode features were introduced.   One of them was found to be of more
       nuisance than benefit: the automagic (and silent) "UTF-8-ification" of filehandles, including
       the standard filehandles, if the user's locale settings indicated use of UTF-8.

       For example, if you had "en_US.UTF-8" as your locale, your STDIN and STDOUT were
       automatically "UTF-8", in other words an implicit binmode(..., ":utf8") was made.  This meant
       that trying to print, say, chr(0xff), ended up printing the bytes 0xc3 0xbf.  Hardly what you
       had in mind unless you were aware of this feature of Perl 5.8.0.  The problem is that the
       vast majority of people weren't: for example in RedHat releases 8 and 9 the default locale
       setting is UTF-8, so all RedHat users got UTF-8 filehandles, whether they wanted it or not.
       The pain was intensified by the Unicode implementation of Perl 5.8.0 (still) having nasty
       bugs, especially related to the use of s/// and tr///.  (Bugs that have been fixed in 5.8.1)

       Therefore a decision was made to backtrack the feature and change it from implicit silent
       default to explicit conscious option.  The new Perl command line option "-C" and its
       counterpart environment variable PERL_UNICODE can now be used to control how Perl and Unicode
       interact at interfaces like I/O and for example the command line arguments.  See "-C" in
       perlrun and "PERL_UNICODE" in perlrun for more information.

   Unsafe signals again available
       In Perl 5.8.0 the so-called "safe signals" were introduced.  This means that Perl no longer
       handles signals immediately but instead "between opcodes", when it is safe to do so.  The
       earlier immediate handling easily could corrupt the internal state of Perl, resulting in
       mysterious crashes.

       However, the new safer model has its problems too.  Because now an opcode, a basic unit of
       Perl execution, is never interrupted but instead let to run to completion, certain operations
       that can take a long time now really do take a long time.  For example, certain network
       operations have their own blocking and timeout mechanisms, and being able to interrupt them
       immediately would be nice.

       Therefore perl 5.8.1 introduces a "backdoor" to restore the pre-5.8.0 (pre-5.7.3, really)
       signal behaviour.  Just set the environment variable PERL_SIGNALS to "unsafe", and the old
       immediate (and unsafe) signal handling behaviour returns.  See "PERL_SIGNALS" in perlrun and
       "Deferred Signals (Safe Signals)" in perlipc.

       In completely unrelated news, you can now use safe signals with POSIX::SigAction.  See
       "POSIX::SigAction" in POSIX.

   Tied Arrays with Negative Array Indices
       Formerly, the indices passed to "FETCH", "STORE", "EXISTS", and "DELETE" methods in tied
       array class were always non-negative.  If the actual argument was negative, Perl would call
       FETCHSIZE implicitly and add the result to the index before passing the result to the tied
       array method.  This behaviour is now optional.  If the tied array class contains a package
       variable named $NEGATIVE_INDICES which is set to a true value, negative values will be passed
       to "FETCH", "STORE", "EXISTS", and "DELETE" unchanged.

   local ${$x}
       The syntaxes

               local ${$x}
               local @{$x}
               local %{$x}

       now do localise variables, given that the $x is a valid variable name.

   Unicode Character Database 4.0.0
       The copy of the Unicode Character Database included in Perl 5.8 has been updated to 4.0.0
       from 3.2.0.  This means for example that the Unicode character properties are as in Unicode
       4.0.0.

   Deprecation Warnings
       There is one new feature deprecation.  Perl 5.8.0 forgot to add some deprecation warnings,
       these warnings have now been added.  Finally, a reminder of an impending feature removal.

       (Reminder) Pseudo-hashes are deprecated (really)

       Pseudo-hashes were deprecated in Perl 5.8.0 and will be removed in Perl 5.10.0, see
       perl58delta for details.  Each attempt to access pseudo-hashes will trigger the warning
       "Pseudo-hashes are deprecated".  If you really want to continue using pseudo-hashes but not
       to see the deprecation warnings, use:

           no warnings 'deprecated';

       Or you can continue to use the fields pragma, but please don't expect the data structures to
       be pseudohashes any more.

       (Reminder) 5.005-style threads are deprecated (really)

       5.005-style threads (activated by "use Thread;") were deprecated in Perl 5.8.0 and will be
       removed after Perl 5.8, see perl58delta for details.  Each 5.005-style thread creation will
       trigger the warning "5.005 threads are deprecated".  If you really want to continue using the
       5.005 threads but not to see the deprecation warnings, use:

           no warnings 'deprecated';

       (Reminder) The $* variable is deprecated (really)

       The $* variable controlling multi-line matching has been deprecated and will be removed after
       5.8.  The variable has been deprecated for a long time, and a deprecation warning "Use of $*
       is deprecated" is given, now the variable will just finally be removed.  The functionality
       has been supplanted by the "/s" and "/m" modifiers on pattern matching.  If you really want
       to continue using the $*-variable but not to see the deprecation warnings, use:

           no warnings 'deprecated';

   Miscellaneous Enhancements
       "map" in void context is no longer expensive. "map" is now context aware, and will not
       construct a list if called in void context.

       If a socket gets closed by the server while printing to it, the client now gets a SIGPIPE.
       While this new feature was not planned, it fell naturally out of PerlIO changes, and is to be
       considered an accidental feature.

       PerlIO::get_layers(FH) returns the names of the PerlIO layers active on a filehandle.

       PerlIO::via layers can now have an optional UTF8 method to indicate whether the layer wants
       to "auto-:utf8" the stream.

       utf8::is_utf8() has been added as a quick way to test whether a scalar is encoded internally
       in UTF-8 (Unicode).

Modules and Pragmata
   Updated Modules And Pragmata
       The following modules and pragmata have been updated since Perl 5.8.0:

       base
       B::Bytecode
           In much better shape than it used to be.  Still far from perfect, but maybe worth a try.

       B::Concise
       B::Deparse
       Benchmark
           An optional feature, ":hireswallclock", now allows for high resolution wall clock times
           (uses Time::HiRes).

       ByteLoader
           See B::Bytecode.

       bytes
           Now has bytes::substr.

       CGI
       charnames
           One can now have custom character name aliases.

       CPAN
           There is now a simple command line frontend to the CPAN.pm module called cpan.

       Data::Dumper
           A new option, Pair, allows choosing the separator between hash keys and values.

       DB_File
       Devel::PPPort
       Digest::MD5
       Encode
           Significant updates on the encoding pragma functionality (tr/// and the DATA filehandle,
           formats).

           If a filehandle has been marked as to have an encoding, unmappable characters are
           detected already during input, not later (when the corrupted data is being used).

           The ISO 8859-6 conversion table has been corrected (the 0x30..0x39 erroneously mapped to
           U+0660..U+0669, instead of U+0030..U+0039).  The GSM 03.38 conversion did not handle
           escape sequences correctly.  The UTF-7 encoding has been added (making Encode feature-
           complete with Unicode::String).

       fields
       libnet
       Math::BigInt
           A lot of bugs have been fixed since v1.60, the version included in Perl v5.8.0.
           Especially noteworthy are the bug in Calc that caused div and mod to fail for some large
           values, and the fixes to the handling of bad inputs.

           Some new features were added, e.g. the broot() method, you can now pass parameters to
           config() to change some settings at runtime, and it is now possible to trap the creation
           of NaN and infinity.

           As usual, some optimizations took place and made the math overall a tad faster. In some
           cases, quite a lot faster, actually. Especially alternative libraries like
           Math::BigInt::GMP benefit from this. In addition, a lot of the quite clunky routines like
           fsqrt() and flog() are now much much faster.

       MIME::Base64
       NEXT
           Diamond inheritance now works.

       Net::Ping
       PerlIO::scalar
           Reading from non-string scalars (like the special variables, see perlvar) now works.

       podlators
       Pod::LaTeX
       PodParsers
       Pod::Perldoc
           Complete rewrite.  As a side-effect, no longer refuses to startup when run by root.

       Scalar::Util
           New utilities: refaddr, isvstring, looks_like_number, set_prototype.

       Storable
           Can now store code references (via B::Deparse, so not foolproof).

       strict
           Earlier versions of the strict pragma did not check the parameters implicitly passed to
           its "import" (use) and "unimport" (no) routine.  This caused the false idiom such as:

                   use strict qw(@ISA);
                   @ISA = qw(Foo);

           This however (probably) raised the false expectation that the strict refs, vars and subs
           were being enforced (and that @ISA was somehow "declared").  But the strict refs, vars,
           and subs are not enforced when using this false idiom.

           Starting from Perl 5.8.1, the above will cause an error to be raised.  This may cause
           programs which used to execute seemingly correctly without warnings and errors to fail
           when run under 5.8.1.  This happens because

                   use strict qw(@ISA);

           will now fail with the error:

                   Unknown 'strict' tag(s) '@ISA'

           The remedy to this problem is to replace this code with the correct idiom:

                   use strict;
                   use vars qw(@ISA);
                   @ISA = qw(Foo);

       Term::ANSIcolor
       Test::Harness
           Now much more picky about extra or missing output from test scripts.

       Test::More
       Test::Simple
       Text::Balanced
       Time::HiRes
           Use of nanosleep(), if available, allows mixing subsecond sleeps with alarms.

       threads
           Several fixes, for example for join() problems and memory leaks.  In some platforms (like
           Linux) that use glibc the minimum memory footprint of one ithread has been reduced by
           several hundred kilobytes.

       threads::shared
           Many memory leaks have been fixed.

       Unicode::Collate
       Unicode::Normalize
       Win32::GetFolderPath
       Win32::GetOSVersion
           Now returns extra information.

Utility Changes
       The "h2xs" utility now produces a more modern layout: Foo-Bar/lib/Foo/Bar.pm instead of
       Foo/Bar/Bar.pm.  Also, the boilerplate test is now called t/Foo-Bar.t instead of t/1.t.

       The Perl debugger (lib/perl5db.pl) has now been extensively documented and bugs found while
       documenting have been fixed.

       "perldoc" has been rewritten from scratch to be more robust and feature rich.

       "perlcc -B" works now at least somewhat better, while "perlcc -c" is rather more broken.
       (The Perl compiler suite as a whole continues to be experimental.)

New Documentation
       perl573delta has been added to list the differences between the (now quite obsolete)
       development releases 5.7.2 and 5.7.3.

       perl58delta has been added: it is the perldelta of 5.8.0, detailing the differences between
       5.6.0 and 5.8.0.

       perlartistic has been added: it is the Artistic License in pod format, making it easier for
       modules to refer to it.

       perlcheat has been added: it is a Perl cheat sheet.

       perlgpl has been added: it is the GNU General Public License in pod format, making it easier
       for modules to refer to it.

       perlmacosx has been added to tell about the installation and use of Perl in Mac OS X.

       perlos400 has been added to tell about the installation and use of Perl in OS/400 PASE.

       perlreref has been added: it is a regular expressions quick reference.

Installation and Configuration Improvements
       The Unix standard Perl location, /usr/bin/perl, is no longer overwritten by default if it
       exists.  This change was very prudent because so many Unix vendors already provide a
       /usr/bin/perl, but simultaneously many system utilities may depend on that exact version of
       Perl, so better not to overwrite it.

       One can now specify installation directories for site and vendor man and HTML pages, and site
       and vendor scripts.  See INSTALL.

       One can now specify a destination directory for Perl installation by specifying the DESTDIR
       variable for "make install".  (This feature is slightly different from the previous
       "Configure -Dinstallprefix=...".)  See INSTALL.

       gcc versions 3.x introduced a new warning that caused a lot of noise during Perl compilation:
       "gcc -Ialreadyknowndirectory (warning: changing search order)".  This warning has now been
       avoided by Configure weeding out such directories before the compilation.

       One can now build subsets of Perl core modules by using the Configure flags
       "-Dnoextensions=..." and "-Donlyextensions=...", see INSTALL.

   Platform-specific enhancements
       In Cygwin Perl can now be built with threads ("Configure -Duseithreads").  This works with
       both Cygwin 1.3.22 and Cygwin 1.5.3.

       In newer FreeBSD releases Perl 5.8.0 compilation failed because of trying to use malloc.h,
       which in FreeBSD is just a dummy file, and a fatal error to even try to use.  Now malloc.h is
       not used.

       Perl is now known to build also in Hitachi HI-UXMPP.

       Perl is now known to build again in LynxOS.

       Mac OS X now installs with Perl version number embedded in installation directory names for
       easier upgrading of user-compiled Perl, and the installation directories in general are more
       standard.  In other words, the default installation no longer breaks the Apple-provided Perl.
       On the other hand, with "Configure -Dprefix=/usr" you can now really replace the Apple-
       supplied Perl (please be careful).

       Mac OS X now builds Perl statically by default.  This change was done mainly for faster
       startup times.  The Apple-provided Perl is still dynamically linked and shared, and you can
       enable the sharedness for your own Perl builds by "Configure -Duseshrplib".

       Perl has been ported to IBM's OS/400 PASE environment.  The best way to build a Perl for PASE
       is to use an AIX host as a cross-compilation environment.  See README.os400.

       Yet another cross-compilation option has been added: now Perl builds on OpenZaurus, a Linux
       distribution based on Mandrake + Embedix for the Sharp Zaurus PDA.  See the Cross/README
       file.

       Tru64 when using gcc 3 drops the optimisation for toke.c to "-O2" because of gigantic memory
       use with the default "-O3".

       Tru64 can now build Perl with the newer Berkeley DBs.

       Building Perl on WinCE has been much enhanced, see README.ce and README.perlce.

Selected Bug Fixes
   Closures, eval and lexicals
       There have been many fixes in the area of anonymous subs, lexicals and closures.  Although
       this means that Perl is now more "correct", it is possible that some existing code will break
       that happens to rely on the faulty behaviour.  In practice this is unlikely unless your code
       contains a very complex nesting of anonymous subs, evals and lexicals.

   Generic fixes
       If an input filehandle is marked ":utf8" and Perl sees illegal UTF-8 coming in when doing
       "<FH>", if warnings are enabled a warning is immediately given - instead of being silent
       about it and Perl being unhappy about the broken data later.  (The ":encoding(utf8)" layer
       also works the same way.)

       binmode(SOCKET, ":utf8") only worked on the input side, not on the output side of the socket.
       Now it works both ways.

       For threaded Perls certain system database functions like getpwent() and getgrent() now grow
       their result buffer dynamically, instead of failing.  This means that at sites with lots of
       users and groups the functions no longer fail by returning only partial results.

       Perl 5.8.0 had accidentally broken the capability for users to define their own
       uppercase<->lowercase Unicode mappings (as advertised by the Camel).  This feature has been
       fixed and is also documented better.

       In 5.8.0 this

               $some_unicode .= <FH>;

       didn't work correctly but instead corrupted the data.  This has now been fixed.

       Tied methods like FETCH etc. may now safely access tied values, i.e.  resulting in a
       recursive call to FETCH etc.  Remember to break the recursion, though.

       At startup Perl blocks the SIGFPE signal away since there isn't much Perl can do about it.
       Previously this blocking was in effect also for programs executed from within Perl.  Now Perl
       restores the original SIGFPE handling routine, whatever it was, before running external
       programs.

       Linenumbers in Perl scripts may now be greater than 65536, or 2**16.  (Perl scripts have
       always been able to be larger than that, it's just that the linenumber for reported errors
       and warnings have "wrapped around".)  While scripts that large usually indicate a need to
       rethink your code a bit, such Perl scripts do exist, for example as results from generated
       code.  Now linenumbers can go all the way to 4294967296, or 2**32.

   Platform-specific fixes
       Linux

       •   Setting $0 works again (with certain limitations that Perl cannot do much about: see "$0"
           in perlvar)

       HP-UX

       •   Setting $0 now works.

       VMS

       •   Configuration now tests for the presence of "poll()", and IO::Poll now uses the vendor-
           supplied function if detected.

       •   A rare access violation at Perl start-up could occur if the Perl image was installed with
           privileges or if there was an identifier with the subsystem attribute set in the
           process's rightslist.  Either of these circumstances triggered tainting code that
           contained a pointer bug.  The faulty pointer arithmetic has been fixed.

       •   The length limit on values (not keys) in the %ENV hash has been raised from 255 bytes to
           32640 bytes (except when the PERL_ENV_TABLES setting overrides the default use of logical
           names for %ENV).  If it is necessary to access these long values from outside Perl, be
           aware that they are implemented using search list logical names that store the value in
           pieces, each 255-byte piece (up to 128 of them) being an element in the search list. When
           doing a lookup in %ENV from within Perl, the elements are combined into a single value.
           The existing VMS-specific ability to access individual elements of a search list logical
           name via the $ENV{'foo;N'} syntax (where N is the search list index) is unimpaired.

       •   The piping implementation now uses local rather than global DCL symbols for inter-process
           communication.

       •   File::Find could become confused when navigating to a relative directory whose name
           collided with a logical name.  This problem has been corrected by adding directory syntax
           to relative path names, thus preventing logical name translation.

       Win32

       •   A memory leak in the fork() emulation has been fixed.

       •   The return value of the ioctl() built-in function was accidentally broken in 5.8.0.  This
           has been corrected.

       •   The internal message loop executed by perl during blocking operations sometimes
           interfered with messages that were external to Perl.  This often resulted in blocking
           operations terminating prematurely or returning incorrect results, when Perl was
           executing under environments that could generate Windows messages.  This has been
           corrected.

       •   Pipes and sockets are now automatically in binary mode.

       •   The four-argument form of select() did not preserve $! (errno) properly when there were
           errors in the underlying call.  This is now fixed.

       •   The "CR CR LF" problem of has been fixed, binmode(FH, ":crlf") is now effectively a no-
           op.

New or Changed Diagnostics
       All the warnings related to pack() and unpack() were made more informative and consistent.

   Changed "A thread exited while %d threads were running"
       The old version

           A thread exited while %d other threads were still running

       was misleading because the "other" included also the thread giving the warning.

   Removed "Attempt to clear a restricted hash"
       It is not illegal to clear a restricted hash, so the warning was removed.

   New "Illegal declaration of anonymous subroutine"
       You must specify the block of code for "sub".

   Changed "Invalid range "%s" in transliteration operator"
       The old version

           Invalid [] range "%s" in transliteration operator

       was simply wrong because there are no "[] ranges" in tr///.

   New "Missing control char name in \c"
       Self-explanatory.

   New "Newline in left-justified string for %s"
       The padding spaces would appear after the newline, which is probably not what you had in
       mind.

   New "Possible precedence problem on bitwise %c operator"
       If you think this

           $x & $y == 0

       tests whether the bitwise AND of $x and $y is zero, you will like this warning.

   New "Pseudo-hashes are deprecated"
       This warning should have been already in 5.8.0, since they are.

   New "read() on %s filehandle %s"
       You cannot read() (or sysread()) from a closed or unopened filehandle.

   New "5.005 threads are deprecated"
       This warning should have been already in 5.8.0, since they are.

   New "Tied variable freed while still in use"
       Something pulled the plug on a live tied variable, Perl plays safe by bailing out.

   New "To%s: illegal mapping '%s'"
       An illegal user-defined Unicode casemapping was specified.

   New "Use of freed value in iteration"
       Something modified the values being iterated over.  This is not good.

Changed Internals
       These news matter to you only if you either write XS code or like to know about or hack Perl
       internals (using Devel::Peek or any of the "B::" modules counts), or like to run Perl with
       the "-D" option.

       The embedding examples of perlembed have been reviewed to be up to date and consistent: for
       example, the correct use of PERL_SYS_INIT3() and PERL_SYS_TERM().

       Extensive reworking of the pad code (the code responsible for lexical variables) has been
       conducted by Dave Mitchell.

       Extensive work on the v-strings by John Peacock.

       UTF-8 length and position cache: to speed up the handling of Unicode (UTF-8) scalars, a cache
       was introduced.  Potential problems exist if an extension bypasses the official APIs and
       directly modifies the PV of an SV: the UTF-8 cache does not get cleared as it should.

       APIs obsoleted in Perl 5.8.0, like sv_2pv, sv_catpvn, sv_catsv, sv_setsv, are again
       available.

       Certain Perl core C APIs like cxinc and regatom are no longer available at all to code
       outside the Perl core of the Perl core extensions.  This is intentional.  They never should
       have been available with the shorter names, and if you application depends on them, you
       should (be ashamed and) contact perl5-porters to discuss what are the proper APIs.

       Certain Perl core C APIs like "Perl_list" are no longer available without their "Perl_"
       prefix.  If your XS module stops working because some functions cannot be found, in many
       cases a simple fix is to add the "Perl_" prefix to the function and the thread context
       "aTHX_" as the first argument of the function call.  This is also how it should always have
       been done: letting the Perl_-less forms to leak from the core was an accident.  For cleaner
       embedding you can also force this for all APIs by defining at compile time the cpp define
       PERL_NO_SHORT_NAMES.

       Perl_save_bool() has been added.

       Regexp objects (those created with "qr") now have S-magic rather than R-magic.  This fixed
       regexps of the form /...(??{...;$x})/ to no longer ignore changes made to $x.  The S-magic
       avoids dropping the caching optimization and making (??{...}) constructs obscenely slow (and
       consequently useless).  See also "Magic Variables" in perlguts.  Regexp::Copy was affected by
       this change.

       The Perl internal debugging macros DEBUG() and DEB() have been renamed to PERL_DEBUG() and
       PERL_DEB() to avoid namespace conflicts.

       "-DL" removed (the leaktest had been broken and unsupported for years, use alternative
       debugging mallocs or tools like valgrind and Purify).

       Verbose modifier "v" added for "-DXv" and "-Dsv", see perlrun.

New Tests
       In Perl 5.8.0 there were about 69000 separate tests in about 700 test files, in Perl 5.8.1
       there are about 77000 separate tests in about 780 test files.  The exact numbers depend on
       the Perl configuration and on the operating system platform.

Known Problems
       The hash randomisation mentioned in "Incompatible Changes" is definitely problematic: it will
       wake dormant bugs and shake out bad assumptions.

       If you want to use mod_perl 2.x with Perl 5.8.1, you will need mod_perl-1.99_10 or higher.
       Earlier versions of mod_perl 2.x do not work with the randomised hashes.  (mod_perl 1.x works
       fine.)  You will also need Apache::Test 1.04 or higher.

       Many of the rarer platforms that worked 100% or pretty close to it with perl 5.8.0 have been
       left a little bit untended since their maintainers have been otherwise busy lately, and
       therefore there will be more failures on those platforms.  Such platforms include Mac OS
       Classic, IBM z/OS (and other EBCDIC platforms), and NetWare.  The most common Perl platforms
       (Unix and Unix-like, Microsoft platforms, and VMS) have large enough testing and expert
       population that they are doing well.

   Tied hashes in scalar context
       Tied hashes do not currently return anything useful in scalar context, for example when used
       as boolean tests:

               if (%tied_hash) { ... }

       The current nonsensical behaviour is always to return false, regardless of whether the hash
       is empty or has elements.

       The root cause is that there is no interface for the implementors of tied hashes to implement
       the behaviour of a hash in scalar context.

   Net::Ping 450_service and 510_ping_udp failures
       The subtests 9 and 18 of lib/Net/Ping/t/450_service.t, and the subtest 2 of
       lib/Net/Ping/t/510_ping_udp.t might fail if you have an unusual networking setup.  For
       example in the latter case the test is trying to send a UDP ping to the IP address 127.0.0.1.

   B::C
       The C-generating compiler backend B::C (the frontend being "perlcc -c") is even more broken
       than it used to be because of the extensive lexical variable changes.  (The good news is that
       B::Bytecode and ByteLoader are better than they used to be.)

Platform Specific Problems
   EBCDIC Platforms
       IBM z/OS and other EBCDIC platforms continue to be problematic regarding Unicode support.
       Many Unicode tests are skipped when they really should be fixed.

   Cygwin 1.5 problems
       In Cygwin 1.5 the io/tell and op/sysio tests have failures for some yet unknown reason.  In
       1.5.5 the threads tests stress_cv, stress_re, and stress_string are failing unless the
       environment variable PERLIO is set to "perlio" (which makes also the io/tell failure go
       away).

       Perl 5.8.1 does build and work well with Cygwin 1.3: with (uname -a) "CYGWIN_NT-5.0 ...
       1.3.22(0.78/3/2) 2003-03-18 09:20 i686 ..."  a 100% "make test"  was achieved with "Configure
       -des -Duseithreads".

   HP-UX: HP cc warnings about sendfile and sendpath
       With certain HP C compiler releases (e.g. B.11.11.02) you will get many warnings like this
       (lines wrapped for easier reading):

         cc: "/usr/include/sys/socket.h", line 504: warning 562:
           Redeclaration of "sendfile" with a different storage class specifier:
             "sendfile" will have internal linkage.
         cc: "/usr/include/sys/socket.h", line 505: warning 562:
           Redeclaration of "sendpath" with a different storage class specifier:
             "sendpath" will have internal linkage.

       The warnings show up both during the build of Perl and during certain lib/ExtUtils tests that
       invoke the C compiler.  The warning, however, is not serious and can be ignored.

   IRIX: t/uni/tr_7jis.t falsely failing
       The test t/uni/tr_7jis.t is known to report failure under 'make test' or the test harness
       with certain releases of IRIX (at least IRIX 6.5 and MIPSpro Compilers Version 7.3.1.1m), but
       if run manually the test fully passes.

   Mac OS X: no usemymalloc
       The Perl malloc ("-Dusemymalloc") does not work at all in Mac OS X.  This is not that
       serious, though, since the native malloc works just fine.

   Tru64: No threaded builds with GNU cc (gcc)
       In the latest Tru64 releases (e.g. v5.1B or later) gcc cannot be used to compile a threaded
       Perl (-Duseithreads) because the system "<pthread.h>" file doesn't know about gcc.

   Win32: sysopen, sysread, syswrite
       As of the 5.8.0 release, sysopen()/sysread()/syswrite() do not behave like they used to in
       5.6.1 and earlier with respect to "text" mode.  These built-ins now always operate in
       "binary" mode (even if sysopen() was passed the O_TEXT flag, or if binmode() was used on the
       file handle).  Note that this issue should only make a difference for disk files, as sockets
       and pipes have always been in "binary" mode in the Windows port.  As this behavior is
       currently considered a bug, compatible behavior may be re-introduced in a future release.
       Until then, the use of sysopen(), sysread() and syswrite() is not supported for "text" mode
       operations.

Future Directions
       The following things might happen in future.  The first publicly available releases having
       these characteristics will be the developer releases Perl 5.9.x, culminating in the Perl
       5.10.0 release.  These are our best guesses at the moment: we reserve the right to rethink.

       •   PerlIO will become The Default.  Currently (in Perl 5.8.x) the stdio library is still
           used if Perl thinks it can use certain tricks to make stdio go really fast.  For future
           releases our goal is to make PerlIO go even faster.

       •   A new feature called assertions will be available.  This means that one can have code
           called assertions sprinkled in the code: usually they are optimised away, but they can be
           enabled with the "-A" option.

       •   A new operator "//" (defined-or) will be available.  This means that one will be able to
           say

               $a // $b

           instead of

              defined $a ? $a : $b

           and

              $c //= $d;

           instead of

              $c = $d unless defined $c;

           The operator will have the same precedence and associativity as "||".  A source code
           patch against the Perl 5.8.1 sources will be available in CPAN as
           authors/id/H/HM/HMBRAND/dor-5.8.1.diff.

       •   "unpack()" will default to unpacking the $_.

       •   Various Copy-On-Write techniques will be investigated in hopes of speeding up Perl.

       •   CPANPLUS, Inline, and Module::Build will become core modules.

       •   The ability to write true lexically scoped pragmas will be introduced.

       •   Work will continue on the bytecompiler and byteloader.

       •   v-strings as they currently exist are scheduled to be deprecated.  The v-less form
           (1.2.3) will become a "version object" when used with "use", "require", and $VERSION.
           $^V will also be a "version object" so the printf("%vd",...) construct will no longer be
           needed.  The v-ful version (v1.2.3) will become obsolete.  The equivalence of strings and
           v-strings (e.g.  that currently 5.8.0 is equal to "\5\8\0") will go away.  There may be
           no deprecation warning for v-strings, though: it is quite hard to detect when v-strings
           are being used safely, and when they are not.

       •   5.005 Threads Will Be Removed

       •   The $* Variable Will Be Removed (it was deprecated a long time ago)

       •   Pseudohashes Will Be Removed

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 AT perl.org to be analysed by
       the Perl porting team.  You can browse and search the Perl 5 bugs at http://bugs.perl.org/

SEE ALSO
       The Changes file for exhaustive details on what changed.

       The INSTALL file for how to build Perl.

       The README file for general stuff.

       The Artistic and Copying files for copyright information.



perl v5.34.0                                 2026-06-23                              PERL581DELTA(1)