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perldelta - what is new for perl v5.19.8


This document describes differences between the 5.19.7 release and the 5.19.8 release.

If you are upgrading from an earlier release such as 5.19.6, first read perl5197delta, which describes differences between 5.19.6 and 5.19.7.

Core Enhancements

New \p{Unicode} regular expression pattern property

This is a synonym for \p{Any} and matches the set of Unicode-defined code points 0 - 0x10FFFF.

Incompatible Changes

do can no longer be used to call subroutines

The do SUBROUTINE(LIST) form has resulted in a deprecation warning since Perl v5.0.0, and is now a syntax error.

\p{}, \P{} matching has changed for non-Unicode code points.

\p{} and \P{} are defined by Unicode only on Unicode-defined code points (U+0000 through U+10FFFF). Their behavior on matching these legal Unicode code points is unchanged, but there are changes for code points 0x110000 and above. Previously, Perl treated the result of matching \p{} and \P{} against these as undef, which translates into "false". For \P{}, this was then complemented into "true". A warning was supposed to be raised when this happened. However, various optimizations could prevent the warning, and the results were often counter-intuitive, with both a match and its seeming complement being false. Now all non-Unicode code points are treated as typical unassigned Unicode code points. This generally is more Do-What-I-Mean. A warning is raised only if the results are arguably different from a strict Unicode approach, and from what Perl used to do. Code that needs to be strictly Unicode compliant can make this warning fatal, and then Perl always raises the warning.

Details are in "Beyond Unicode code points" in perlunicode.

\p{All} has been expanded to match all possible code points

The Perl-defined regular expression pattern element \p{All}, unused on CPAN, used to match just the Unicode code points; now it matches all possible code points; that is, it is equivalent to qr/./s. Thus \p{All} is no longer synonymous with \p{Any}, which continues to match just the Unicode code points, as Unicode says it should.


XXX Any deprecated features, syntax, modules etc. should be listed here.

Module removals

XXX Remove this section if inapplicable.

The following modules will be removed from the core distribution in a future release, and will at that time need to be installed from CPAN. Distributions on CPAN which require these modules will need to list them as prerequisites.

The core versions of these modules will now issue "deprecated"-category warnings to alert you to this fact. To silence these deprecation warnings, install the modules in question from CPAN.

Note that these are (with rare exceptions) fine modules that you are encouraged to continue to use. Their disinclusion from core primarily hinges on their necessity to bootstrapping a fully functional, CPAN-capable Perl installation, not usually on concerns over their design.

    XXX Note that deprecated modules should be listed here even if they are listed as an updated module in the "Modules and Pragmata" section.

Modules and Pragmata

New Modules and Pragmata

  • IO::Socket::IP has been (tentatively) added to core at version 0.26.

Updated Modules and Pragmata

  • perl5db.pl has been upgraded from version 1.42 to 1.43

    Fix a crash in tab completion, where available. [perl #120827]

    The debugger tests no longer open two handles to the same output file, making them more robust. [perl #118817]

  • base has been upgraded from version 2.20 to 2.21.

    The stricter load failure tests added in 2.20 now allow for ${^LAST_FH} being set.

  • constant has been upgraded from version 1.30 to 1.31.

  • DynaLoader has been upgraded from version 1.22 to 1.24.

  • Encode has been upgraded from version 2.55 to 2.57.

    UTF-8 is no longer used in the C source (which some compilers didn't like), and some POD errors have been fixed in the documentation.

  • Errno has been upgraded from version 1.20_01 to 1.20_02.

  • ExtUtils::CBuilder has been upgraded from version 0.280212 to 0.280213.

  • ExtUtils::MakeMaker has been upgraded from version 6.84 to 6.86.

  • File::Copy has been upgraded from version 2.28 to 2.29.

  • Hash::Util::FieldHash has been upgraded from version 1.13 to 1.14.

  • inc::latest has been upgraded from version 0.4203 to 0.4204. NOTE: inc::latest is deprecated and may be removed from a future version of Perl.

  • IO::Socket::UNIX has been upgraded from version 1.25 to 1.26.

    Removed a warning about an ancient behaviour change and filled out the SYNOPSIS. [perl #120981]

  • The libnet module collection has been upgraded from version 1.23 to 1.24.

    The handling of CRLF characters in Net::FTP has been fixed.

  • List::Util has been upgraded from version 1.35 to 1.36.

  • Module::Build has been upgraded from version 0.4203 to 0.4204. NOTE: Module::Build is deprecated and may be removed from a future version of Perl.

  • Module::CoreList has been upgraded from version 3.02 to 3.04.

  • Module::Load has been upgraded from version 0.24 to 0.28.

  • Module::Load::Conditional has been upgraded from version 0.58 to 0.60.

  • Perl::OSType has been upgraded from version 1.006 to 1.007.

  • PerlIO::encoding has been upgraded from version 0.17 to 0.18.

  • Pod::Perldoc has been upgraded from version 3.20 to 3.21.

  • POSIX has been upgraded from version 1.37 to 1.38_01.

  • Scalar::Util has been upgraded from version 1.35 to 1.36.

  • threads::shared has been upgraded from version 1.45 to 1.46.

  • Time::Piece has been upgraded from version 1.24 to 1.27.

  • Unicode::UCD has been upgraded from version 0.55 to 0.57.

  • version has been upgraded from version 0.9904 to 0.9907.

  • warnings has been upgraded from version 1.20 to 1.21.

  • XSLoader has been upgraded from version 0.16 to 0.17.


Changes to Existing Documentation

  • perlunicode has been updated to reflect Bidi_Class changes in Unicode 6.3.


The following additions or changes have been made to diagnostic output, including warnings and fatal error messages. For the complete list of diagnostic messages, see perldiag.

New Warnings

  • %s on a reference is now experimental

    The "auto-deref" feature is now experimental.

    Starting in v5.14.0, it was possible to use push, pop, keys, and other built-in functions not only on aggregate types, but on references to them. The feature was not deployed to its original intended specification, and now may become redundant to postfix dereferencing. It has always been categorized as an experimental feature, and in v5.20.0 is carries a warning as such.

    Warnings will now be issued at compile time when these operations are detected.

      no if $] >= 5.01908, warnings => "experimental::autoderef";

    Consider, though, replacing the use of these features, as they may change behavior again before becoming stable.

  • Matched non-Unicode code point 0x%X against Unicode property; may not be portable. This replaces the message "Code point 0x%X is not Unicode, all \p{} matches fail; all \P{} matches succeed".

Utility Changes


  • perlbug now has a -p option for attaching patches with a bug report.

  • perlbug now does input in the encoding of the current locale and output raw.

Configuration and Compilation

  • Distinct library basenames with d_libname_unique.

    When compiling perl with this option, the library files for XS modules are named something "unique" -- for example, Hash/Util/Util.so becomes Hash/Util/PL_Hash__Util.so. This behavior is similar to what currently happens on VMS, and serves as groundwork for the Android port.

  • sysroot option to indicate the logical root directory under gcc and clang.

    When building with this option set, both Configure and the compilers search for all headers and libraries under this new sysroot, instead of /.

    This is a huge time saver if cross-compiling, but can also help on native builds if your toolchain's files have non-standard locations.

Platform Support

  • Code related to supporting sfio has been removed.

    Perl 5.004 added support to use the native API of sfio, AT&T's Safe/Fast I/O library. This code still built with v5.8.0, albeit with many regression tests failing, but was inadvertently broken before the v5.8.1 release, meaning that it has not worked on any version of Perl released since then. In over a decade we have received no bug reports about this, hence it is clear that no-one is using this functionality on any version of Perl that is still supported to any degree.

Platform-Specific Notes


recv() on a connected handle would populate the returned sender address with whatever happened to be in the working buffer. recv() now uses a workaround similar to the Win32 recv() wrapper and returns an empty string when recvfrom(2) doesn't modify the supplied address length. [perl #118843]

Internal Changes

newATTRSUB is now a macro

The public API newATTRSUB was previously a macro to the private function Perl_newATTRSUB. Function Perl_newATTRSUB has been removed. newATTRSUB is now macro to a different internal function.

Changes in warnings raised by utf8n_to_uvchr()

This bottom level function decodes the first character of a UTF-8 string into a code point. It is accessible to XS level code, but it's discouraged from using it directly. There are higher level functions that call this that should be used instead, such as "utf8_to_uvchr_buf" in perlapi. For completeness though, this documents some changes to it. Now, tests for malformations are done before any tests for other potential issues. One of those issues involves code points so large that they have never appeared in any official standard (the current standard has scaled back the highest acceptable code point from earlier versions). It is possible (though not done in CPAN) to warn and/or forbid these code points, while accepting smaller code points that are still above the legal Unicode maximum. The warning message for this now includes the code point if representable on the machine. Previously it always displayed raw bytes, which is what it still does for non-representable code points.

Selected Bug Fixes

  • In v5.19.6, do CORE() was inadvertently changed from being interpreted as do-file (i.e., do +CORE()) to do-sub (i.e., &CORE()). It has now been changed back.

  • v5.19.7 inadvertently caused freed scalars to be passed to subroutines in @INC if it contained multiple subs. This has been fixed. [perl #120657]

  • Individually-tied elements of @INC (as in tie $INC[0]...) are now handled correctly. Formerly, whether a sub returned by such a tied element would be treated as a sub depended on whether a FETCH had occurred previously.

  • getc on a byte-sized handle after the same getc operator had been used on a utf8 handle used to treat the bytes as utf8, resulting in erratic behavior (e.g., malformed UTF-8 warnings).

  • An initial { at the beginning of a format argument line was always interpreted as the beginning of a block prior to v5.18. In Perl v5.18, it started being treated as an ambiguous token. The parser would guess whether it was supposed to be an anonymous hash constructor or a block based on the contents. Now the previous behavious has been restored. [perl #119973]

  • In Perl v5.18 undef *_; goto &sub and local *_; goto &sub started crashing. This has been fixed. [perl #119949]


Perl 5.19.8 represents approximately 4 weeks of development since Perl 5.19.7 and contains approximately 38,000 lines of changes across 420 files from 26 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 5.19.8:

Abigail, Alan Hourihane, Brian Fraser, Brian Gottreu, Chris 'BinGOs' Williams, Christian Millour, Craig A. Berry, Dagfinn Ilmari Mannsåker, Daniel Dragan, David Mitchell, Dominic Hargreaves, Father Chrysostomos, H.Merijn Brand, James E Keenan, Jess Robinson, John Peacock, Karl Williamson, Martin McGrath, Matthew Horsfall, Nicholas Clark, Ricardo Signes, Shlomi Fish, Steve Hay, Tobias Leich, Tony Cook, 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 https://rt.perl.org/ . 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.