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perldelta - what is new for perl v5.15.8


This document describes differences between the 5.15.7 release and the 5.15.8 release.

If you are upgrading from an earlier release such as 5.15.6, first read perl5157delta, which describes differences between 5.15.6 and 5.15.7.


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Core Enhancements

Improved ability to mix locales and Unicode, including UTF-8 locales

An optional parameter has been added to use locale

 use locale ':not_characters';

which tells Perl to use all but the LC_CTYPE and LC_COLLATE portions of the current locale. Instead, the character set is assumed to be Unicode. This allows locales and Unicode to be seamlessly mixed, including the increasingly frequent UTF-8 locales. When using this hybrid form of locales, the :locale layer to the open pragma can be used to interface with the file system, and there are CPAN modules available for ARGV and environment variable conversions.

Full details are in perllocale.

New function fc and corresponding escape sequence \F for Unicode foldcase

Unicode foldcase is an extension to lowercase that gives better results when comparing two strings case-insensitively. It has long been used internally in regular expression /i matching. Now it is available explicitly through the new fc function call (enabled by "use feature 'fc'", or use v5.16, or explicitly callable via CORE::fc) or through the new \F sequence in double-quotish strings.

Full details are in "fc" in perlfunc.

_ in subroutine prototypes

The _ character in subroutine prototypes is now allowed before @ or %.

Supports (almost) Unicode 6.1

Besides the addition of whole new scripts, and new characters in existing scripts, this new version of Unicode, as always, makes some changes to existing characters. One change that may trip up some applications is that the General Category of two characters in the Latin-1 range, PILCROW SIGN and SECTION SIGN, has been changed from Other_Symbol to Other_Punctuation. The same change has been made for a character in each of Tibetan, Ethiopic, and Aegean. The code points U+3248..U+324F (CIRCLED NUMBER TEN ON BLACK SQUARE through CIRCLED NUMBER EIGHTY ON BLACK SQUARE) have had their General Category changed from Other_Symbol to Other_Numeric. The Line Break property has changes for Hebrew and Japanese; and as a consequence of other changes in 6.1, the Perl regular expression construct \X now works differently for some characters in Thai and Lao.

New aliases (synonyms) have been defined for many property values; these, along with the previously existing ones, are all cross indexed in perluniprops.

The return value of charnames::viacode() is affected by other changes:

 Code point      Old Name             New Name
   U+000A    LINE FEED (LF)        LINE FEED
   U+000C    FORM FEED (FF)        FORM FEED
   U+0085    NEXT LINE (NEL)       NEXT LINE
   U+008E    SINGLE-SHIFT 2        SINGLE-SHIFT-2
   U+008F    SINGLE-SHIFT 3        SINGLE-SHIFT-3
   U+0091    PRIVATE USE 1         PRIVATE USE-1
   U+0092    PRIVATE USE 2         PRIVATE USE-2

Perl will accept any of these names as input, but charnames::viacode() now returns the new name of each pair. The change for U+2118 is considered by Unicode to be a correction, that is the original name was a mistake (but again, it will remain forever valid to use it to refer to U+2118). But most of these changes are the fallout of the mistake Unicode 6.0 made in naming a character used in Japanese cell phones to be "BELL", which conflicts with the long standing industry use of (and Unicode's recommendation to use) that name to mean the ASCII control character at U+0007. As a result, that name has been deprecated in Perl since v5.14; and any use of it will raise a warning message (unless turned off). The name "ALERT" is now the preferred name for this code point, with "BEL" being an acceptable short form. The name for the new cell phone character, at code point U+1F514, remains undefined in this version of Perl (hence we don't quite implement all of Unicode 6.1), but starting in v5.18, BELL will mean this character, and not U+0007.

Unicode has taken steps to make sure that this sort of mistake does not happen again. The Standard now includes all the generally accepted names and abbreviations for control characters, whereas previously it didn't (though there were recommended names for most of them, which Perl used). This means that most of those recommended names are now officially in the Standard. Unicode did not recommend names for the four code points listed above between U+008E and U+008F, and in standardizing them Unicode subtly changed the names that Perl had previously given them, by replacing the final blank in each name by a hyphen. Unicode also officially accepts names that Perl had deprecated, such as FILE SEPARATOR. Now the only deprecated name is BELL. Finally, Perl now uses the new official names instead of the old (now considered obsolete) names for the first four code points in the list above (the ones which have the parentheses in them).

Now that the names have been placed in the Unicode standard, these kinds of changes should not happen again, though corrections, such as to U+2118, are still possible.

Unicode also added some name abbreviations, which Perl now accepts: SP for SPACE; TAB for CHARACTER TABULATION; NEW LINE, END OF LINE, NL, and EOL for LINE FEED; LOCKING-SHIFT ONE for SHIFT OUT; LOCKING-SHIFT ZERO for SHIFT IN; and ZWNBSP for ZERO WIDTH NO-BREAK SPACE.

More details on this version of Unicode are provided in http://www.unicode.org/versions/Unicode6.1.0/.

Added is_utf8_char_buf()

This function is designed to replace the deprecated "is_utf8_char()" function. It includes an extra parameter to make sure it doesn't read past the end of the input buffer.


Use is_utf8_char_buf() and not is_utf8_char()

The latter function is now deprecated because its API is insufficient to guarantee that it doesn't read (up to 12 bytes in the worst case) beyond the end of its input string. See is_utf8_char_buf().

Incompatible Changes

[ List each incompatible change as a =head2 entry ]

Special blocks called in void context

Special blocks (BEGIN, CHECK, INIT, UNITCHECK, END) are now called in void context. This avoids wasteful copying of the result of the last statement [perl #108794].

The overloading pragma and regexp objects

With no overloading, regular expression objects returned by qr// are now stringified as "Regexp=REGEXP(0xbe600d)" instead of the regular expression itself [perl #108780].

Two XS typemap Entries removed

Two presumably unused XS typemap entries have been removed from the core typemap: T_DATAUNIT and T_CALLBACK. If you are, against all odds, a user of these, please see the instructions on how to regain them in perlxstypemap.

Unicode 6.1 has incompatibilities with Unicode 6.0

These are detailed in "Supports (almost) Unicode 6.1" above.

Changed returns for some properties in Unicode::UCD::prop_invmap()

The return values for prop_invmap have been changed for some properties to make the returned lists significantly smaller. This allows those lists to be searched faster.

This function was introduced earlier in the v5.15 series of releases, and the API will not be considered stable until v5.16.

See "prop_invmap()" in Unicode::UCD for details on the new interface.

$$ and getppid() no longer emulate POSIX semantics under LinuxThreads

The POSIX emulation of $$ and getppid() under the obsolete LinuxThreads implementation has been removed (the $$ emulation was actually removed in v5.15.0). This only impacts users of Linux 2.4 and users of Debian GNU/kFreeBSD up to and including 6.0, not the vast majority of Linux installations that use NPTL threads.

This means that getppid() like $$ is now always guaranteed to return the OS's idea of the current state of the process, not perl's cached version of it.

See the documentation for $$ for details.

$<, $>, $( and $) are no longer cached

Similarly to the changes to $$ and getppid() the internal caching of $<, $>, $( and $) has been removed.

When we cached these values our idea of what they were would drift out of sync with reality if someone (e.g. someone embedding perl) called sete?[ug]id() without updating PL_e?[ug]id. Having to deal with this complexity wasn't worth it given how cheap the gete?[ug]id() system call is.

This change will break a handful of CPAN modules that use the XS-level PL_uid, PL_gid, PL_euid or PL_egid variables.

The fix for those breakages is to use PerlProc_gete?[ug]id() to retrieve them (e.g. PerlProc_getuid()), and not to assign to PL_e?[ug]id if you change the UID/GID/EUID/EGID. There is no longer any need to do so since perl will always retrieve the up-to-date version of those values from the OS.

Which Non-ASCII characters get quoted by quotemeta and \Q has changed

This is unlikely to result in a real problem, as Perl does not attach special meaning to any non-ASCII character, so it is currently irrelevant which are quoted or not. This change fixes bug [perl #77654] and bring Perl's behavior more into line with Unicode's recommendations. See "quotemeta" in perlfunc.



This function is deprecated because it could read beyond the end of the input string. Use the new is_utf8_char_buf() instead.

Modules and Pragmata

New Modules and Pragmata

  • PerlIO::mmap 0.010 has been added to the Perl core.

    The mmap PerlIO layer is no longer implemented by perl itself, but has been moved out into the new PerlIO::mmap module.

Updated Modules and Pragmata

  • arybase has been upgraded from version 0.03 to version 0.04.

    List slices no longer modify items on the stack belonging to outer lists [perl #109570].

  • B has been upgraded from version 1.33 to version 1.34.

    B::COP now has a stashflags method, corresponding to a new internal field added in 5.15.4 [perl #108860].

  • B::Deparse has been upgraded from version 1.11 to 1.12.

  • Carp has been upgraded from version 1.24 to version 1.25.

    It now puts a dot after the file and line number, just like errors from die [perl #106538].

  • Compress::Raw::Bzip2 has been upgraded from version 2.045 to 2.048.

  • Compress::Raw::Zlib has been upgraded from version 2.045 to 2.048.

  • Compress::Zlib has been upgraded from version 2.046 to version 2.048.

  • CPAN::Meta has been upgraded from version 2.113640 to 2.120351.

    Work around a memory leak bug involving version objects in boolean context.

  • CPAN::Meta::YAML has been upgraded from version 0.005 to 0.007.

  • CPANPLUS has been upgraded from version 0.9116 to 0.9118.

  • CPANPLUS::Dist::Build has been upgraded from version 0.60 to 0.62.

  • Data::Dumper has been upgraded from version 2.135_04 to 2.135_05.

  • DB_File has been upgraded from version 1.824 to 1.826.

  • diagnostics has been upgraded from version 1.27 to 1.28.

    When searching for perldiag.pod, it no longer uses paths that were only relevant on Perl 5.004 and earlier.

  • English has been upgraded from version 1.04 to 1.05.

  • ExtUtils::Install has been upgraded from version 1.57 to 1.58.

  • ExtUtils::ParseXS has been upgraded from version 3.12 to 3.16.

    The new version comes with important tools for sharing typemaps between different CPAN distributions.

  • File::Copy has been upgraded from version 2.21 to 2.23.

    It no longer emits warnings when copying files with newlines in their names [perl #109104].

  • File::Glob has been upgraded from version 1.16 to 1.17.

  • Filter::Util::Call has been upgraded from version 1.39 to 1.40.

  • IPC::Cmd has been upgraded from version 0.72 to 0.76.

  • Math::Complex has been upgraded from version 1.58 to 1.59.

    This avoids a new core warning.

  • Module::Metadata has been upgraded from version 1.000007 to 1.000009.

    Adds provides method to generate a CPAN META provides data structure correctly; use of package_versions_from_directory is discouraged.

  • Opcode has been upgraded from version 1.22 to 1.23.

  • overload has been upgraded from version 1.17 to 1.18.

  • Parse::CPAN::Meta has been upgraded from version 1.4401 to 1.4402.

  • perlfaq has been upgraded from version 5.0150038 to 5.0150039.

  • Pod::Functions has been upgraded from version 1.04 to 1.05.

    Functions.pm is now generated at perl build time from annotations in perlfunc.pod. This will ensure that Pod::Functions and perlfunc remain in synchronisation.

  • Pod::Html has been upgraded from version 1.13 to 1.14.

  • Pod::Parser has been upgraded from version 1.37 to 1.51.

  • POSIX has been upgraded from version 1.28 to 1.30.

  • re has been upgraded from version 0.18 to 0.19.

  • Safe has been upgraded from version 2.30 to 2.31.

  • Socket has been upgraded from version 1.97 to 1.98.

  • Term::Cap has been upgraded from version 1.12 to 1.13.

  • Term::ReadLine has been upgraded from version 1.07 to 1.08.

    Term::ReadLine now supports any event loop, including unpublished ones and simple IO::Select loops without the need to rewrite existing code for any particular framework [perl #108470].

  • Time::HiRes has been upgraded from version 1.9724 to 1.9725.

    Time::HiRes::stat() no longer corrupts the Perl stack.

  • Unicode::UCD has been upgraded from version 0.39 to 0.41.

    The only change is to fix a formatting error in the Pod.

  • Version::Requirements has been upgraded from version 0.101021 to 0.101022.

  • warnings has been upgraded from version 1.12 to 1.13.

  • XS::Typemap has been upgraded from version 0.07 to 0.08.


New Documentation


The new manual describes the XS typemapping mechanism in unprecedented detail and combines new documentation with information extracted from perlxs and the previously unofficial list of all core typemaps.


  • t/porting/pending-author.t has been added, to avoid the problem of make test passing 100%, but the subsequent git commit causing t/porting/authors.t to fail, because it uses a "new" e-mail address.

    This test is only run if one is building inside a git checkout, and one has made local changes. Otherwise it's skipped.

  • t/porting/perlfunc.t has been added, to test that changes to pod/perlfunc.pod do not inadvertently break the build of Pod::Functions.

  • The test suite for typemaps has been extended to cover a larger fraction of the core typemaps.

Platform Support

Platform-Specific Notes


Since version 1.7, Cygwin supports native UTF-8 paths. If Perl is built under that environment, directory and filenames will be UTF-8 encoded.

Cygwin does not initialize all original Win32 environment variables. See README.cygwin for a discussion of Cygwin::sync_winenv() and further links.


The build on VMS now allows names of the resulting symbols in C code for Perl longer than 31 characters. Symbols like Perl__it_was_the_best_of_times_it_was_the_worst_of_times can now be created freely without causing the VMS linker to seize up.

Selected Bug Fixes

  • ~~ now correctly handles the precedence of Any~~Object, and is not tricked by an overloaded object on the left-hand side.

  • stat _ no longer warns about unopened filehandles [perl #71002].

  • stat on an unopened filehandle now warns consistently, instead of skipping the warning at times.

  • A change in an earlier 5.15 release caused warning hints to propagate into do $file. This has been fixed [rt.cpan.org #72767].

  • Starting with 5.12.0, Perl used to get its internal bookkeeping muddled up after assigning ${ qr// } to a hash element and locking it with Hash::Util. This could result in double frees, crashes or erratic behaviour.

  • In 5.15.7, some typeglobs in the CORE namespace were made read-only by mistake. This has been fixed [rt.cpan.org #74289].

  • -t now works when stacked with other filetest operators [perl #77388].

  • Stacked filetest operators now only call FETCH once on a tied argument.

  • /.*/g would sometimes refuse to match at the end of a string that ends with "\n". This has been fixed [perl #109206].

  • m/[[:ascii:]]/i and /\p{ASCII}/i now match identically (when not under a differing locale). This fixes a regression introduced in 5.14 in which the first expression could match characters outside of ASCII, such as the KELVIN SIGN.

  • Method calls whose arguments were all surrounded with my() or our() (as in $object->method(my($a,$b))) used to force lvalue context on the subroutine. This would prevent lvalue methods from returning certain values. Due to lvalue fixes earlier in the 5.15.x series, it would also prevent non-lvalue methods from being called [perl #109264].

  • The SvPVutf8 C function no longer tries to modify its argument, resulting in errors [perl #108994].

  • SvPVutf8 now works properly with magical variables.

  • SvPVbyte now works properly non-PVs.

  • /[[:ascii:]]/ and /[[:blank:]]/ now use locale rules under use locale when the platform supports that. Previously, they used the platform's native character set.

  • A regression introduced in 5.13.6 was fixed. This involved an inverted bracketed character class in a regular expression that consisted solely of a Unicode property, that property wasn't getting inverted outside the Latin1 range.

  • quotemeta now quotes consistently the same non-ASCII characters under use feature 'unicode_strings', regardless of whether the string is encoded in UTF-8 or not, hence fixing the last vestiges (we hope) of the infamous "The "Unicode Bug"" in perlunicode. [perl #77654].

    Which of these code points is quoted has changed, based on Unicode's recommendations. See "quotemeta" in perlfunc for details.

Known Problems

This is a list of some significant unfixed bugs, which are regressions from either 5.14.0 or 5.15.7.

  • eval { 'fork()' } is broken on Windows [perl #109718]

    This is a known test failure to be fixed before 5.16.0.


Perl 5.15.8 represents approximately 4 weeks of development since Perl 5.15.7 and contains approximately 61,000 lines of changes across 480 files from 36 authors.

Perl continues to flourish into its third decade thanks to a vibrant community of users and developers. The following people are known to have contributed the improvements that became Perl 5.15.8:

Abhijit Menon-Sen, Alan Haggai Alavi, Alexandr Ciornii, Andy Dougherty, Brian Fraser, Chris 'BinGOs' Williams, Craig A. Berry, Darin McBride, Dave Rolsky, David Golden, David Leadbeater, David Mitchell, Dominic Hargreaves, Eric Brine, Father Chrysostomos, Florian Ragwitz, H.Merijn Brand, Juerd Waalboer, Karl Williamson, Leon Timmermans, Marc Green, Max Maischein, Nicholas Clark, Paul Evans, Rafael Garcia-Suarez, Rainer Tammer, Reini Urban, Ricardo Signes, Robin Barker, Shlomi Fish, Steffen Müller, Todd Rinaldo, Tony Cook, Yves Orton, Zefram, Ævar Arnfjörð Bjarmason.

The list above is almost certainly incomplete as it is automatically generated from version control history. In particular, it does not include the names of the (very much appreciated) contributors who reported issues to the Perl bug tracker.

Many of the changes included in this version originated in the CPAN modules included in Perl's core. We're grateful to the entire CPAN community for helping Perl to flourish.

For a more complete list of all of Perl's historical contributors, please see the AUTHORS file in the Perl source distribution.

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://rt.perl.org/perlbug/ . There may also be information at http://www.perl.org/ , 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.

If the bug you are reporting has security implications, which make it inappropriate to send to a publicly archived mailing list, then please send it to perl5-security-report@perl.org. This points to a closed subscription unarchived mailing list, which includes all the core committers, who will be able to help assess the impact of issues, figure out a resolution, and help co-ordinate the release of patches to mitigate or fix the problem across all platforms on which Perl is supported. Please only use this address for security issues in the Perl core, not for modules independently distributed on CPAN.


The Changes file for an explanation of how to view 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.