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perldelta - what is new for perl v5.23.7


This document describes differences between the 5.23.6 release and the 5.23.7 release.

If you are upgrading from an earlier release such as 5.23.5, first read perl5236delta, which describes differences between 5.23.5 and 5.23.6.

Core Enhancements

New \b{lb} boundary in regular expressions

lb stands for Line Break. It is a Unicode property that determines where a line of text is suitable to break (typically so that it can be output without overflowing the available horizontal space). This capability has long been furnished by the Unicode::LineBreak module, but now a light-weight, non-customizable version that is suitable for many purposes is in core Perl.


fix out of boundary access in Win32 path handling

This is CVE-2015-8608. For more information see [perl #126755]

fix loss of taint in canonpath

This is CVE-2015-8607. For more information see [perl #126862]

Avoid accessing uninitialized memory in win32 crypt()

Added validation that will detect both a short salt and invalid characters in the salt. [perl #126922]

Incompatible Changes

qr/\b{wb}/ is now tailored to Perl expectations

This is now more suited to be a drop-in replacement for plain \b, but giving better results for parsing natural language. Previously it strictly followed the current Unicode rules which calls for it to match between each white space character. Now it doesn't generally match within spans of white space, behaving like \b does. See "\b{wb}" in perlrebackslash

Modules and Pragmata

Updated Modules and Pragmata

  • The cpan/podlators/ bundle has been upgraded from version 2.28 to 4.04.

  • B has been upgraded from version 1.61 to 1.62.

  • B::Deparse has been upgraded from version 1.36 to 1.37.

  • Benchmark has been upgraded from version 1.21 to 1.22.

  • bignum has been upgraded from version 0.41 to 0.42.

  • Data::Dumper has been upgraded from version 2.159 to 2.160.

  • ExtUtils::ParseXS has been upgraded from version 3.30 to 3.31.

  • ExtUtils::Typemaps has been upgraded from version 3.30 to 3.31.

  • File::Find has been upgraded from version 1.32 to 1.33.

  • File::Spec has been upgraded from version 3.60 to 3.62.

  • Math::BigInt has been upgraded from version 1.999710 to 1.999715.

  • Math::BigInt::FastCalc has been upgraded from version 0.38 to 0.40.

  • Math::BigRat has been upgraded from version 0.260801 to 0.260802.

  • Module::CoreList has been upgraded from version 5.20151220 to 5.20160120.

  • Pod::Usage has been upgraded from version 1.67 to 1.68.

  • Test::Harness has been upgraded from version 3.35 to 3.36.

  • Unicode::Normalize has been upgraded from version 1.24 to 1.25.

  • Unicode::UCD has been upgraded from version 0.63 to 0.64.

  • utf8 has been upgraded from version 1.18 to 1.19.


Changes to Existing Documentation


  • Fixed a broken example where = was used instead of == in conditional in do/while example.



  • Move sample commands into verbatim paragraphs.

  • Improve hyperlinks for all email addresses, RT tickets and commit hashes.

  • Consistently refer to bisect.pl as Porting/bisect.pl

  • Miscellaneous grammar and POD fixes.


  • Fix some examples to be strict clean.


  • Clarify that in languages like Japanese and Thai, dictionary lookup is required to determine word boundaries.


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.

Changes to Existing Diagnostics

  • Accessing the IO part of a glob as FILEHANDLE instead of IO is no longer deprecated. It is discouraged to encourage uniformity (so that, for example, one can grep more easily) but it will not be removed. [perl #127060]

Configuration and Compilation

  • Configure no longer probes for libnm by default. Originally this was the "New Math" library, but the name has been re-used by the GNOME NetworkManager. [perl #127131]

  • No longer generate EBCDIC POSIX-BC tables. We don't believe anyone is using Perl and POSIX-BC at this time, and by not generating these tables it saves time during development, and makes the resulting tar ball smaller.

  • The Win32 miniperl now has a real getcwd which increases build performance resulting in getcwd() being 605x faster in Win32 miniperl.

Platform Support

Platform-Specific Notes

  • On VMS, the math function prototypes in math.h are now visible under C++. Now building the POSIX extension with C++ will no longer crash.

  • VMS has had setenv/unsetenv since v7.0 (released in 1996), Perl_vmssetenv now always uses setenv/unsetenv.

  • Try more crypt algorithms in the tests, for OpenBSD. OpenBSD implements the Blowfish algorithm, but not the MD5 one used by glibc. Enhance the crypt and taint tests to try both algorithms. If neither works, fall back to no algorithm. The Blowfish salt is taken from the OpenBSD crypt(3) page.

  • Use the fdclose() function from FreeBSD if it is available. [perl #126847]

Internal Changes

  • The obscure PL_timesbuf variable, effectively a vestige of Perl 1, has been removed. It was documented as deprecated in Perl 5.20, with a statement that it would be removed early in the 5.21.x series; that has now finally happened. [perl #121351]

  • Remove unwarranted assertion in Perl_newATTRSUB_x(). If a stub subroutine definition with a prototype has been seen, then any subsequent stub (or definition) of the same subroutine with an attribute was causing an assertion failure because of a null pointer. [perl #126845]

  • Replace :: with __ in ExtUtils::ParseXS like it's done for parameters/return values. This is more consistent, and simplifies writing XS code wrapping C++ classes into a nested Perl namespace (it requires only a typedef for Foo__Bar rather than two, one for Foo_Bar and the other for Foo::Bar).

  • Deprecate the to_utf8_case() function, see http://nntp.perl.org/group/perl.perl5.porters/233287.

Selected Bug Fixes

  • A regression that allowed undeclared barewords in hash keys to work despite strictures has been fixed. [perl #126981]

  • Calls to the placeholder &PL_sv_yes used internally when an import() or unimport() method isn't found now correctly handle scalar context. [perl #126042]

  • Fixed some problems introduced in 5.23.2 with list assignment dealing with magic and XS functions returning their arguments. [perl #126633]

  • Report more context when we see an array where we expect to see an operator and avoid an assertion failure. [perl #123737]

  • Modifying an array that was previously a package @ISA no longer causes assertion failures or crashes. [perl #123788]

  • Retain binary compatibility across plain and DEBUGGING perl builds. [perl #127212]

  • Avoid leaking memory when setting $ENV{foo} on darwin. [perl #126240]

Known Problems

  • Statically building perl is not currently working due to a problem related to multiple definitions of the cp1252_encoding in the Encode module.


Perl 5.23.7 represents approximately 4 weeks of development since Perl 5.23.6 and contains approximately 87,000 lines of changes across 450 files from 21 authors.

Excluding auto-generated files, documentation and release tools, there were approximately 67,000 lines of changes to 320 .pm, .t, .c and .h files.

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 5.23.7:

Aaron Crane, Andreas König, Andy Dougherty, Chris 'BinGOs' Williams, Craig A. Berry, Dagfinn Ilmari Mannsåker, Daniel Dragan, David Golden, David Mitchell, James E Keenan, Jarkko Hietaniemi, Karen Etheridge, Karl Williamson, Lukas Mai, Mattia Barbon, Ricardo Signes, Stevan Little, Steve Hay, Todd Rinaldo, Tom Hukins, Tony Cook.

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.