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perl571delta (1)


perl571delta - what's new for perl v5.7.1


Please see following description for synopsis


Perl Programmers Reference Guide                  PERL571DELTA(1)

     perl571delta - what's new for perl v5.7.1

     This document describes differences between the 5.7.0
     release and the 5.7.1 release.

     (To view the differences between the 5.6.0 release and the
     5.7.0 release, see perl570delta.)

Security Vulnerability Closed
     (This change was already made in 5.7.0 but bears repeating

     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 April 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
     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 all the Perl 5.7 releases (and will be gone
     also from the maintenance release 5.6.1), so that particular
     vulnerability isn't there anymore.  However, further
     security vulnerabilities are, unfortunately, always
     possible.  The suidperl code is being reviewed and if deemed
     too risky to continue to be supported, it may be completely
     removed from future releases.  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 ).

Incompatible Changes
     o   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".

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     o   The list of filenames from glob() (or <...>) is now by
         default sorted alphabetically to be csh-compliant.
         (bsd_glob() does still sort platform natively, ASCII or
         EBCDIC, unless GLOB_ALPHASORT is specified.)

Core Enhancements
  AUTOLOAD Is Now Lvaluable
     AUTOLOAD is now lvaluable, meaning that you can add the
     :lvalue attribute to AUTOLOAD subroutines and you can assign
     to the AUTOLOAD return value.

  PerlIO is Now The Default
     o   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($fh,'>:crlf :utf8', $path) || ...

         or on already opened handles via extended "binmode":


         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.

     o   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" :


         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 for more
         information.  In future releases this naming may change.

     o   File handles can translate character encodings from/to
         Perl's internal Unicode form on read/write via the

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         ":encoding()" layer.

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

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

     o   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.

     o   The list form of "open" is now implemented for pipes (at
         least on Unix):

            open($fh,"-|", 'cat', '/etc/motd')

         creates a pipe, and runs the equivalent of exec('cat',
         '/etc/motd') in the child process.

     o   The following builtin functions are now overridable:
         chop(), chomp(), each(), keys(), pop(), push(), shift(),
         splice(), unshift().

     o   Formats now support zero-padded decimal fields.

     o   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 into often slightly faster and always less lossy
         arithmetics. (Previously Perl always preferred floating
         point numbers in its math.)

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

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

         will print "bar foo\n"; This feature helps in writing
         internationalised software.

     o   Unicode in general should be now much more usable.
         Unicode can be used in hash keys, Unicode in regular
         expressions should work now, Unicode in tr/// should
         work now (though tr/// seems to be a particularly tricky
         to get right, so you have been warned)

     o   The Unicode Character Database coming with Perl has been

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         upgraded to Unicode 3.1.  For more information, see , and

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

     o   The Unicode character classes \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.)

  Signals Are Now Safe
     Perl used to be fragile in that signals arriving at
     inopportune moments could corrupt Perl's internal state.

Modules and Pragmata
  New Modules
     o   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

         See B::Concise for more information.

     o   Class::ISA, by Sean Burke, for reporting the search path
         for a class's ISA tree, has been added.

         See Class::ISA for more information.

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

     o   Digest, a frontend module for calculating digests
         (checksums), from Gisle Aas, has been added.

         See Digest for more information.

     o   Digest::MD5 for calculating MD5 digests (checksums), by
         Gisle Aas, has been added.

             use Digest::MD5 'md5_hex';

             $digest = md5_hex("Thirsty Camel");

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

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

         See Digest::MD5 for more information.

     o   Encode, by Nick Ing-Simmons, provides a mechanism to
         translate between different character encodings.
         Support for Unicode, ISO-8859-*, ASCII, CP*, KOI8-R, and
         three variants of EBCDIC are compiled in to the module.
         Several other encodings (like Japanese, Chinese, and
         MacIntosh encodings) are included and will be loaded at

         Any encoding supported by Encode module is also
         available to the ":encoding()" layer if PerlIO is used.

         See Encode for more information.

     o   Filter::Simple is an easy-to-use frontend to
         Filter::Util::Call, from Damian Conway.

             # in

             package MyFilter;

             use Filter::Simple sub {
                 while (my ($from, $to) = splice @_, 0, 2) {


             # in user's code:

             use MyFilter qr/red/ => 'green';

             print "red\n";   # this code is filtered, will print "green\n"
             print "bored\n"; # this code is filtered, will print "bogreen\n"

             no MyFilter;

             print "red\n";   # this code is not filtered, will print "red\n"

         See Filter::Simple for more information.

     o   Filter::Util::Call, by Paul Marquess, provides you with
         the framework to write Source Filters in Perl.  For most
         uses the frontend Filter::Simple is to be preferred.

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         See Filter::Util::Call for more information.

     o   Locale::Constants, Locale::Country, Locale::Currency,
         and Locale::Language, from Neil Bowers, have been added.
         They provide the codes for various locale standards,
         such as "fr" for France, "usd" for US Dollar, and "jp"
         for Japanese.

             use Locale::Country;

             $country = code2country('jp');               # $country gets 'Japan'
             $code    = country2code('Norway');           # $code gets 'no'

         See Locale::Constants, Locale::Country,
         Locale::Currency, and Locale::Language for more

     o   MIME::Base64, by Gisle Aas, allows you to encode data in

             use MIME::Base64;

             $encoded = encode_base64('Aladdin:open sesame');
             $decoded = decode_base64($encoded);

             print $encoded, "\n"; # "QWxhZGRpbjpvcGVuIHNlc2FtZQ=="

         See MIME::Base64 for more information.

     o   MIME::QuotedPrint, by Gisle Aas, allows you to encode
         data in quoted-printable encoding.

             use MIME::QuotedPrint;

             $encoded = encode_qp("Smiley in Unicode: \x{263a}");
             $decoded = decode_qp($encoded);

             print $encoded, "\n"; # "Smiley in Unicode: =263A"

         MIME::QuotedPrint has been enhanced to provide the basic
         methods necessary to use it with PerlIO::Via as in :

             use MIME::QuotedPrint;

         See MIME::QuotedPrint for more information.

     o   PerlIO::Scalar, by Nick Ing-Simmons, provides the
         implementation of IO to "in memory" Perl scalars as
         discussed above.  It also serves as an example of a
         loadable layer.  Other future possibilities include
         PerlIO::Array and PerlIO::Code.  See PerlIO::Scalar for

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         more information.

     o   PerlIO::Via, by Nick Ing-Simmons, acts as a PerlIO layer
         and wraps PerlIO layer functionality provided by a class
         (typically implemented in perl code).

             use MIME::QuotedPrint;

         This will automatically convert everything output to $fh
         to Quoted-Printable.  See PerlIO::Via for more

     o   Pod::Text::Overstrike, by Joe Smith, has been added.  It
         converts POD data to formatted overstrike text.  See
         Pod::Text::Overstrike for more information.

     o   Switch from Damian Conway has been added.  Just by

             use Switch;

         you have "switch" and "case" available in Perl.

             use Switch;

             switch ($val) {

                         case 1          { print "number 1" }
                         case "a"        { print "string a" }
                         case [1..10,42] { print "number in list" }
                         case (@array)   { print "number in list" }
                         case /\w+/      { print "pattern" }
                         case qr/\w+/    { print "pattern" }
                         case (%hash)    { print "entry in hash" }
                         case (\%hash)   { print "entry in hash" }
                         case (\&sub)    { print "arg to subroutine" }
                         else            { print "previous case not true" }

         See Switch for more information.

     o   Text::Balanced from Damian Conway has been added, for
         extracting delimited text sequences from strings.

             use Text::Balanced 'extract_delimited';

             ($a, $b) = extract_delimited("'never say never', he never said", "'", '');

         $a will be "'never say never'", $b will be ', he never

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         In addition to extract_delimited() there are also
         extract_bracketed(), extract_quotelike(),
         extract_codeblock(), extract_variable(),
         extract_tagged(), extract_multiple(),
         gen_delimited_pat(), and gen_extract_tagged().  With
         these you can implement rather advanced parsing
         algorithms.  See Text::Balanced for more information.

     o   Tie::RefHash::Nestable, by Edward Avis, allows storing
         hash references (unlike the standard Tie::RefHash)  The
         module is contained within Tie::RefHash.

     o   XS::Typemap, by Tim Jenness, is a test extension that
         exercises XS typemaps.  Nothing gets installed but for
         extension writers the code is worth studying.

  Updated And Improved Modules and Pragmata
     o   B::Deparse should be now more robust.  It still far from
         providing a full round trip for any random piece of Perl
         code, though, and is under active development: expect
         more robustness in 5.7.2.

     o   Class::Struct can now define the classes in compile

     o   Math::BigFloat has undergone much fixing, and in
         addition the fmod() function now supports modulus

         ( The fixed Math::BigFloat module is also available in
         CPAN for those who can't upgrade their Perl: )

     o   Devel::Peek now has an interface for the Perl memory
         statistics (this works only if you are using perl's
         malloc, and if you have compiled with debugging).

     o   IO::Socket has now atmark() method, which returns true
         if the socket is positioned at the out-of-band mark.
         The method is also exportable as a sockatmark()

     o   IO::Socket::INET has support for ReusePort option (if
         your platform supports it).  The Reuse option now has an
         alias, ReuseAddr.  For clarity you may want to prefer

     o   Net::Ping has been enhanced.  There is now "external"
         protocol which uses Net::Ping::External module which
         runs external ping(1) and parses the output.  An alpha
         version of Net::Ping::External is available in CPAN and
         in 5.7.2 the Net::Ping::External may be integrated to

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     o   The "open" pragma allows layers other than ":raw" and
         ":crlf" when using PerlIO.

     o   POSIX::sigaction() is now much more flexible and robust.
         You can now install coderef handlers, 'DEFAULT', and
         'IGNORE' handlers, installing new handlers was not

     o   The Test module has been significantly enhanced.  Its
         use is greatly recommended for module writers.

     o   The utf8:: name space (as in the pragma) provides
         various Perl-callable functions to provide low level
         access to Perl's internal Unicode representation.  At
         the moment only length() has been implemented.

     The following modules have been upgraded from the versions
     at CPAN: CPAN, CGI, DB_File, File::Temp, Getopt::Long,
     Pod::Man, Pod::Text, Storable, Text-Tabs+Wrap.

Performance Enhancements
     o   Hashes now use Bob Jenkins "One-at-a-Time" hashing key
         algorithm (
         ).  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.

     o   unshift() should now be noticeably faster.

Utility Changes
     o   h2xs now produces template README.

     o   s2p has been completely rewritten in Perl.  (It is in
         fact a full implementation of sed in Perl.)

     o   xsubpp now supports OUT keyword.

New Documentation
     Internal replacements for standard C library functions.
     (Interesting only for extension writers and Perl core

     Internals of PerlIO with layers.

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     Documentation on compiling Perl on AIX has been added.  AIX
     has several different C compilers and getting the right
     patch level is essential.  On install README.aix will be
     installed as perlaix.

     Documentation on compiling Perl on the POSIX-BC platform (an
     EBCDIC mainframe environment) has been added.

     This was formerly known as README.posix-bc but the name was
     considered to be too confusing (it has nothing to do with
     the POSIX module or the POSIX standard).  On install
     README.bs2000 will be installed as perlbs2000.

     In perl 5.7.1 (and in the 5.6.1) the MacPerl sources have
     been synchronised with the standard Perl sources.  To
     compile MacPerl some additional steps are required, and this
     file documents those steps.  On install README.macos will be
     installed as perlmacos.

     The README.mpeix has been podified, which means that this
     information about compiling and using Perl on the MPE/iX
     miniframe platform will be installed as perlmpeix.

     README.solaris has been created and Solaris wisdom from
     elsewhere in the Perl documentation has been collected
     there.  On install README.solaris will be installed as

     The README.vos has been podified, which means that this
     information about compiling and using Perl on the Stratus
     VOS miniframe platform will be installed as perlvos.

     Documentation on how to use the Perl source repository has
     been added.

Installation and Configuration Improvements
     o   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.

     o   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

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         exact, the use64bitall is ignored.)

     o   APPLLIB_EXP, a less-know 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.

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

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

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

     o   AIX dynamic loading should be now better supported.

     o   After a long pause, AmigaOS has been verified to be
         happy with Perl.

     o   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.

     o   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.

     o   Mac OS Classic (MacPerl has of course been available
         since perl 5.004 but now the source code bases of
         standard Perl and MacPerl have been synchronised)

     o   NCR MP-RAS is now supported.

     o   NonStop-UX is now supported.

     o   Amdahl UTS is now supported.

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

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  Generic Improvements
     o   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.

     o   Some new Configure symbols, useful for extension

                 For struct cmsghdr.

                 Whether fcntl() can be used for file locking.

                 For getpagesize(), though you should prefer

                 For struct msghdr.

                 Whether one needs to use Perl_va_copy() to copy

                 The number of elements in an array needed to
                 hold all the available signals.

                 Whether one needs to access character data
                 aligned by U32 sized pointers.

     o   Removed Configure symbols: the PDP-11 memory model
         settings: huge, large, medium, models.

     o   SOCKS support is now much more robust.

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

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                 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

                 make all test

         and Perl will be built and tested, all in

Selected Bug Fixes
     Numerous memory leaks and uninitialized memory accesses have
     been hunted down.  Most importantly anonymous subs used to
     leak quite a bit.

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

     o   The order of DESTROYs has been made more predictable.

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

     o   Attributes (like :shared) didn't work with our().

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

     o   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.

     o   All but the first argument of the IO syswrite() method
         are now optional.

     o   Tie::ARRAY SPLICE method was broken.

     o   vec() now tries to work with characters <= 255 when
         possible, but it leaves higher character values in
         place.  In that case, if vec() was used to modify the
         string, it is no longer considered to be utf8-encoded.

  Platform Specific Changes and Fixes
     o   Linux previously had problems related to sockaddrlen

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         when using accept(), revcfrom() (in Perl: recv()),
         getpeername(), and getsockname().

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

     o   Windows

         o       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++).

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

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

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

         o       The makefiles now provide a single switch to
                 bulk-enable all the features enabled in
                 ActiveState ActivePerl (a popular binary

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

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

     o   "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.

Changed Internals
     o   Some new APIs: ptr_table_clear(), ptr_table_free(),
         sv_setref_uv().  For the full list of the available APIs
         see perlapi.

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

     o   Perl now uses system malloc instead of Perl malloc on
         all 64-bit platforms, and even in some not-always-64-bit

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         platforms like AIX, IRIX, and Solaris.  This change
         breaks backward compatibility but Perl's malloc has
         problems with large address spaces and also the speed of
         vendors' malloc is generally better in large address
         space machines (Perl's malloc is mostly tuned for

New Tests
     Many new tests have been added.  The most notable is
     probably the lib/1_compile: it is very notable because
     running it takes quite a long time. It test compiles all the
     Perl modules in the distribution.  Please be patient.

Known Problems
     Note that unlike other sections in this document (which
     describe changes since 5.7.0) this section is cumulative
     containing known problems for all the 5.7 releases.

  AIX vac May Produce Buggy Code For Perl
     The AIX C compiler vac version may produce buggy
     code, resulting in few random tests failing, but when the
     failing tests are run by hand, they succeed.  We suggest
     upgrading to at least vac version, that has been
     known to compile Perl correctly.  "lslpp -L|grep vac.C" will
     tell you the vac version.

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

  lib/io_multihomed Fails In LP64-Configured HP-UX
     The lib/io_multihomed test may hang in HP-UX if Perl has
     been configured to be 64-bit. Because other 64-bit platforms
     do not hang in this test, HP-UX is suspect. All other tests
     pass in 64-bit HP-UX. The test attempts to create and
     connect to "multihomed" sockets (sockets which have multiple
     IP addresses).

  Test lib/posix Subtest 9 Fails In LP64-Configured HP-UX
     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.

  lib/b test 19
     The test fails on various platforms (PA64 and IA64 are
     known), but the exact cause is still being investigated.

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

  sigaction test 13 in VMS
     The test is known to fail; whether it's because of VMS of

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     because of faulty test is not known.

  sprintf tests 129 and 130
     The op/sprintf tests 129 and 130 are known to fail on some
     platforms.  Examples include any platform using sfio, and
     Compaq/Tandem's NonStop-UX.  The failing platforms do not
     comply with the ANSI C Standard, line 19ff on page 134 of
     ANSI X3.159 1989 to be exact.  (They produce something else
     than "1" and "-1" when formatting 0.6 and -0.6 using the
     printf format "%.0f", most often they produce "0" and "-0".)

  Failure of Thread tests
     The subtests 19 and 20 of lib/thr5005.t test 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. (Note that
     support for 5.005-style threading remains experimental.)

  Localising a Tied Variable Leaks Memory
         use Tie::Hash;
         tie my %tie_hash => 'Tie::StdHash';


         local($tie_hash{Foo}) = 1; # leaks

     Code like the above is known to leak memory every time the
     local() is executed.

  Self-tying of Arrays and Hashes Is Forbidden
     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 for now forbidden (you will get a
     fatal error even from an attempt).

  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 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) link together at all binaries with different
     ideas about file offsets, all this is platform-dependent.

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  The Compiler Suite Is Still Experimental
     The compiler suite is slowly getting better but is nowhere
     near working order yet.

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
     There may also be information at ,
     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 to be analysed by the Perl porting team.

     See attributes(5) for descriptions of the following

     |Availability   | runtime/perl-512 |
     |Stability      | Uncommitted      |
     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.

     Written by Jarkko Hietaniemi <>, with many
     contributions from The Perl Porters and Perl Users
     submitting feedback and patches.

     Send omissions or corrections to <>.

     This software was built from source available at  The original
     community source was downloaded from

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     Further information about this software can be found on the
     open source community website at

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