New perldelta for 5.27.5

11 files changed, 623 insertions, 175 deletions

diff --git a/MANIFEST b/MANIFEST
index 180fd4f543..5fb06078fe 100644
--- a/MANIFEST
+++ b/MANIFEST
@@ -4970,6 +4970,7 @@ pod/perl5270delta.pod		Perl changes in version 5.27.0
 pod/perl5271delta.pod		Perl changes in version 5.27.1
 pod/perl5272delta.pod		Perl changes in version 5.27.2
 pod/perl5273delta.pod		Perl changes in version 5.27.3
+pod/perl5274delta.pod		Perl changes in version 5.27.4
 pod/perl561delta.pod		Perl changes in version 5.6.1
 pod/perl56delta.pod		Perl changes in version 5.6
 pod/perl581delta.pod		Perl changes in version 5.8.1
diff --git a/Makefile.SH b/Makefile.SH
index 37f3ff8829..730dcca9e1 100755
--- a/Makefile.SH
+++ b/Makefile.SH
@@ -570,7 +570,7 @@ esac
 
 $spitshell >>$Makefile <<'!NO!SUBS!'
 
-perltoc_pod_prereqs = extra.pods pod/perl5274delta.pod pod/perlapi.pod pod/perlintern.pod pod/perlmodlib.pod pod/perluniprops.pod
+perltoc_pod_prereqs = extra.pods pod/perl5275delta.pod pod/perlapi.pod pod/perlintern.pod pod/perlmodlib.pod pod/perluniprops.pod
 generated_pods = pod/perltoc.pod $(perltoc_pod_prereqs)
 generated_headers = uudmap.h bitcount.h mg_data.h
 
@@ -1120,9 +1120,9 @@ pod/perlintern.pod: $(MINIPERL_EXE) autodoc.pl embed.fnc
 pod/perlmodlib.pod: $(MINIPERL_EXE) pod/perlmodlib.PL MANIFEST
 	$(MINIPERL) pod/perlmodlib.PL -q
 
-pod/perl5274delta.pod: pod/perldelta.pod
-	$(RMS) pod/perl5274delta.pod
-	$(LNS) perldelta.pod pod/perl5274delta.pod
+pod/perl5275delta.pod: pod/perldelta.pod
+	$(RMS) pod/perl5275delta.pod
+	$(LNS) perldelta.pod pod/perl5275delta.pod
 
 extra.pods: $(MINIPERL_EXE)
 	-@test ! -f extra.pods || rm -f `cat extra.pods`
diff --git a/pod/.gitignore b/pod/.gitignore
index 276d3648dd..ff8f6f9582 100644
--- a/pod/.gitignore
+++ b/pod/.gitignore
@@ -50,7 +50,7 @@
 /roffitall
 
 # generated
-/perl5274delta.pod
+/perl5275delta.pod
 /perlapi.pod
 /perlintern.pod
 /perlmodlib.pod
diff --git a/pod/perl.pod b/pod/perl.pod
index 2bb6ef1ed2..a98d2e23f5 100644
--- a/pod/perl.pod
+++ b/pod/perl.pod
@@ -181,6 +181,7 @@ aux h2ph h2xs perlbug pl2pm pod2html pod2man splain xsubpp
 
     perlhist		Perl history records
     perldelta		Perl changes since previous version
+    perl5274delta	Perl changes in version 5.27.4
     perl5273delta	Perl changes in version 5.27.3
     perl5272delta	Perl changes in version 5.27.2
     perl5271delta	Perl changes in version 5.27.1
diff --git a/pod/perl5274delta.pod b/pod/perl5274delta.pod
new file mode 100644
index 0000000000..3e36538e3e
--- /dev/null
+++ b/pod/perl5274delta.pod
@@ -0,0 +1,352 @@
+=encoding utf8
+
+=head1 NAME
+
+perl5274delta - what is new for perl v5.27.4
+
+=head1 DESCRIPTION
+
+This document describes differences between the 5.27.3 release and the 5.27.4
+release.
+
+If you are upgrading from an earlier release such as 5.27.2, first read
+L<perl5273delta>, which describes differences between 5.27.2 and 5.27.3.
+
+=head1 Core Enhancements
+
+=head2 In-place editing is now safer
+
+Previously in-place editing would delete or rename the input file
+as soon as you started working on a new file.
+
+Without backups this would result in loss of data if there was an
+error, such as a full disk, when writing to the output file.
+
+This has changed so that the input file isn't replaced until the
+output file has been completely written and successfully closed.
+
+This works by creating a work file in the same directory, which is
+renamed over the input file once the output file is complete.
+
+Incompatibilities:
+
+=over
+
+=item *
+
+Since this renaming needs to only happen once, if you create a thread
+or child process, that renaming will only happen in the original
+thread or process.
+
+=item *
+
+If you change directories while processing a file, and your operating
+system doesn't provide the C<unlinkat()>, C<renameat()> and C<fchmodat()>
+functions, the final rename step may fail.
+
+=back
+
+L<[perl #127663]|https://rt.perl.org/Public/Bug/Display.html?id=127663>
+
+=head1 Security
+
+=head2 [CVE-2017-12837] Heap buffer overflow in regular expression compiler
+
+Compiling certain regular expression patterns with the case-insensitive
+modifier could cause a heap buffer overflow and crash perl.  This has now been
+fixed.
+L<[perl #131582]|https://rt.perl.org/Public/Bug/Display.html?id=131582>
+
+=head2 [CVE-2017-12883] Buffer over-read in regular expression parser
+
+For certain types of syntax error in a regular expression pattern, the error
+message could either contain the contents of a random, possibly large, chunk of
+memory, or could crash perl.  This has now been fixed.
+L<[perl #131598]|https://rt.perl.org/Public/Bug/Display.html?id=131598>
+
+=head2 [CVE-2017-12814] C<$ENV{$key}> stack buffer overflow on Windows
+
+A possible stack buffer overflow in the C<%ENV> code on Windows has been fixed
+by removing the buffer completely since it was superfluous anyway.
+L<[perl #131665]|https://rt.perl.org/Public/Bug/Display.html?id=131665>
+
+=head1 Performance Enhancements
+
+=over 4
+
+=item *
+
+Slightly improved performance when parsing stash names.
+L<[perl #129990]|https://rt.perl.org/Public/Bug/Display.html?id=129990>
+
+=back
+
+=head1 Modules and Pragmata
+
+=head2 Updated Modules and Pragmata
+
+=over 4
+
+=item *
+
+L<attributes> has been upgraded from version 0.3 to 0.31.
+
+=item *
+
+L<File::Glob> has been upgraded from version 1.29 to 1.30.
+
+=item *
+
+L<I18N::Langinfo> has been upgraded from version 0.13 to 0.14.
+This fixes a bug in which the underlying locale was ignored for the
+C<RADIXCHAR> (always was returned as a dot, and the C<THOUSEP> (always
+empty).  Now the locale-appropriate values are returned.
+
+=item *
+
+L<Module::CoreList> has been upgraded from version 5.20170821 to 5.20170920.
+
+=item *
+
+L<sort> has been upgraded from version 2.02 to 2.03.
+
+=item *
+
+L<Term::ReadLine> has been upgraded from version 1.16 to 1.17.
+
+=item *
+
+L<threads> has been upgraded from version 2.17 to 2.18.
+
+=item *
+
+L<VMS::Stdio> has been upgraded from version 2.41 to 2.42.
+
+=back
+
+=head2 Removed Modules and Pragmata
+
+=over 4
+
+=item *
+
+The C<VMS::stdio> compatibility shim has been removed.
+
+=back
+
+=head1 Diagnostics
+
+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 L<perldiag>.
+
+=head2 Changes to Existing Diagnostics
+
+=over 4
+
+=item *
+
+A false-positive warning that was issued when using a
+numerically-quantified sub-pattern in a recursive regex has been
+silenced. L<[perl #131868]|https://rt.perl.org/Public/Bug/Display.html?id=131868>
+
+=back
+
+=head1 Testing
+
+Tests were added and changed to reflect the other additions and changes
+in this release.
+
+=head1 Platform Support
+
+=head2 Platform-Specific Notes
+
+=over 4
+
+=item Darwin
+
+Perl now correctly uses reentrant functions, like C<asctime_r>, on
+versions of Darwin that have support for them.
+
+=back
+
+=head1 Internal Changes
+
+=over 4
+
+=item *
+
+A new function, L<C<Perl_langinfo()>|perlapi/Perl_langinfo> has been
+added.  It is an (almost) drop-in replacement for the system
+C<nl_langinfo(3)>, but works on platforms that lack that; as well as
+being more thread-safe, and hiding some gotchas with locale handling
+from the caller.  Code that uses this, needn't use L<C<localeconv(3)>>
+(and be affected by the gotchas) to find the decimal point, thousands
+separator, or currency symbol.  See L<perlapi/Perl_langinfo>.
+
+=item *
+
+A new API function L<C<sv_rvunweaken()>|perlapi/sv_rvunweaken> has
+been added to complement L<C<sv_rvweaken()>|perlapi/sv_rvweaken>.
+The implementation was taken from L<Scalar::Util/unweaken>.
+
+=item *
+
+A new flag, C<SORTf_UNSTABLE>, has been added. This will allow a
+future commit to make mergesort unstable when the user specifies ‘no
+sort stable’, since it has been decided that mergesort should remain
+stable by default.
+
+=back
+
+=head1 Selected Bug Fixes
+
+=over 4
+
+=item *
+
+The internal stack usage checks introduced in 5.27.2 are now also done
+by the C<entersub> operator when calling XSUBs.  This means we can
+report which XSUB failed to allocate enough stack space.
+L<[perl #131975]|https://rt.perl.org/Public/Bug/Display.html?id=131975>
+
+=item *
+
+Parsing a C<sub> definition could cause a use after free if the C<sub>
+keyword was followed by whitespace including newlines (and comments.)
+L<[perl #131836]|https://rt.perl.org/Public/Bug/Display.html?id=131836>
+
+=item *
+
+The tokenizer now correctly adjusts a parse pointer when skipping
+whitespace in a C< ${identifier} > construct.
+L<[perl #131949]|https://rt.perl.org/Public/Bug/Display.html?id=131949>
+
+=item *
+
+Accesses to C<${^LAST_FH}> no longer assert after using any of a
+variety of I/O operations on a non-glob.
+L<[perl #128263]|https://rt.perl.org/Public/Bug/Display.html?id=128263>
+
+=item *
+
+The C<Copy()>, C<Move()>, C<Zero()> macros and their variants now
+assert if the pointers supplied are C<NULL>.  ISO C considers
+supplying NULL pointers to the functions these macros are built upon
+as undefined behaviour even when their count parameters are zero.
+Based on these assertions and the original bug report three macro
+calls were made conditional.
+L<[perl #131746]|https://rt.perl.org/Public/Bug/Display.html?id=131746>
+L<[perl #131892]|https://rt.perl.org/Public/Bug/Display.html?id=131892>
+
+=item *
+
+The in-place sort optimisation now correctly strengthens weak
+references using the new L<C<sv_rvunweaken()>|perlapi/sv_rvunweaken>
+API function.
+
+=item *
+
+Only the C<=> operator is permitted for defining defaults for
+parameters in subroutine signatures.  Previously other assignment
+operators, e.g. C<+=>, were also permitted.
+L<[perl #131777]|https://rt.perl.org/Public/Bug/Display.html?id=131777>
+
+=item *
+
+Package names are now always included in C<:prototype> warnings
+L<[perl #131833]|https://rt.perl.org/Public/Bug/Display.html?id=131833>
+
+=item *
+
+Creating a thread with no parameters no longer tries to C<Copy()> a
+null pointer. This fixes an assertion failure and allows threaded
+builds to work again.
+
+=item *
+
+The C<je_old_stack_hwm> field, previously only found in the C<jmpenv>
+structure on debugging builds, has been added to non-debug builds as
+well. This fixes an issue with some CPAN modules caused by the size of
+this structure varying between debugging and non-debugging builds.
+L<[perl #131942]|https://rt.perl.org/Public/Bug/Display.html?id=131942>
+
+=item *
+
+The arguments to the C<ninstr()> macro are now correctly parenthesized.
+
+=item *
+
+A NULL pointer dereference in the C<S_regmatch()> function has been
+fixed.
+L<[perl #132017]|https://rt.perl.org/Public/Bug/Display.html?id=132017>
+
+=back
+
+=head1 Acknowledgements
+
+Perl 5.27.4 represents approximately 4 weeks of development since Perl 5.27.3
+and contains approximately 5,000 lines of changes across 140 files from 18
+authors.
+
+Excluding auto-generated files, documentation and release tools, there were
+approximately 3,300 lines of changes to 76 .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 5.27.4:
+
+Abigail, Chris 'BinGOs' Williams, Dagfinn Ilmari Mannsåker, David Mitchell,
+Dominic Hargreaves, Father Chrysostomos, H.Merijn Brand, James E Keenan, Jarkko
+Hietaniemi, John SJ Anderson, Karl Williamson, Lukas Mai, Matthew Horsfall,
+Neil Bowers, Nicolas R., Steve Hay, Tony Cook, Yves Orton.
+
+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 F<AUTHORS> file in the Perl source distribution.
+
+=head1 Reporting Bugs
+
+If you find what you think is a bug, you might check the perl bug database
+at L<https://rt.perl.org/> .  There may also be information at
+L<http://www.perl.org/> , the Perl Home Page.
+
+If you believe you have an unreported bug, please run the L<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 C<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 see
+L<perlsec/SECURITY VULNERABILITY CONTACT INFORMATION>
+for details of how to report the issue.
+
+=head1 Give Thanks
+
+If you wish to thank the Perl 5 Porters for the work we had done in Perl 5,
+you can do so by running the C<perlthanks> program:
+
+    perlthanks
+
+This will send an email to the Perl 5 Porters list with your show of thanks.
+
+=head1 SEE ALSO
+
+The F<Changes> file for an explanation of how to view exhaustive details on
+what changed.
+
+The F<INSTALL> file for how to build Perl.
+
+The F<README> file for general stuff.
+
+The F<Artistic> and F<Copying> files for copyright information.
+
+=cut
diff --git a/pod/perldelta.pod b/pod/perldelta.pod
index fe20b6cb32..6b0e2a4d45 100644
--- a/pod/perldelta.pod
+++ b/pod/perldelta.pod
@@ -2,135 +2,175 @@
 
 =head1 NAME
 
-perldelta - what is new for perl v5.27.4
+[ this is a template for a new perldelta file.  Any text flagged as XXX needs
+to be processed before release. ]
+
+perldelta - what is new for perl v5.27.5
 
 =head1 DESCRIPTION
 
-This document describes differences between the 5.27.3 release and the 5.27.4
+This document describes differences between the 5.27.4 release and the 5.27.5
 release.
 
-If you are upgrading from an earlier release such as 5.27.2, first read
-L<perl5273delta>, which describes differences between 5.27.2 and 5.27.3.
+If you are upgrading from an earlier release such as 5.27.3, first read
+L<perl5274delta>, which describes differences between 5.27.3 and 5.27.4.
+
+=head1 Notice
+
+XXX Any important notices here
 
 =head1 Core Enhancements
 
-=head2 In-place editing is now safer
+XXX New core language features go here.  Summarize user-visible core language
+enhancements.  Particularly prominent performance optimisations could go
+here, but most should go in the L</Performance Enhancements> section.
 
-Previously in-place editing would delete or rename the input file
-as soon as you started working on a new file.
+[ List each enhancement as a =head2 entry ]
 
-Without backups this would result in loss of data if there was an
-error, such as a full disk, when writing to the output file.
+=head1 Security
 
-This has changed so that the input file isn't replaced until the
-output file has been completely written and successfully closed.
+XXX Any security-related notices go here.  In particular, any security
+vulnerabilities closed should be noted here rather than in the
+L</Selected Bug Fixes> section.
 
-This works by creating a work file in the same directory, which is
-renamed over the input file once the output file is complete.
+[ List each security issue as a =head2 entry ]
 
-Incompatibilities:
+=head1 Incompatible Changes
 
-=over
+XXX For a release on a stable branch, this section aspires to be:
 
-=item *
+    There are no changes intentionally incompatible with 5.XXX.XXX
+    If any exist, they are bugs, and we request that you submit a
+    report.  See L</Reporting Bugs> below.
 
-Since this renaming needs to only happen once, if you create a thread
-or child process, that renaming will only happen in the original
-thread or process.
+[ List each incompatible change as a =head2 entry ]
 
-=item *
+=head1 Deprecations
 
-If you change directories while processing a file, and your operating
-system doesn't provide the C<unlinkat()>, C<renameat()> and C<fchmodat()>
-functions, the final rename step may fail.
+XXX Any deprecated features, syntax, modules etc. should be listed here.
 
-=back
+=head2 Module removals
 
-L<[perl #127663]|https://rt.perl.org/Public/Bug/Display.html?id=127663>
+XXX Remove this section if inapplicable.
 
-=head1 Security
+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 C<"deprecated">-category
+warnings to alert you to this fact.  To silence these deprecation warnings,
+install the modules in question from CPAN.
 
-=head2 [CVE-2017-12837] Heap buffer overflow in regular expression compiler
+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.
 
-Compiling certain regular expression patterns with the case-insensitive
-modifier could cause a heap buffer overflow and crash perl.  This has now been
-fixed.
-L<[perl #131582]|https://rt.perl.org/Public/Bug/Display.html?id=131582>
+=over
 
-=head2 [CVE-2017-12883] Buffer over-read in regular expression parser
+=item XXX
 
-For certain types of syntax error in a regular expression pattern, the error
-message could either contain the contents of a random, possibly large, chunk of
-memory, or could crash perl.  This has now been fixed.
-L<[perl #131598]|https://rt.perl.org/Public/Bug/Display.html?id=131598>
+XXX Note that deprecated modules should be listed here even if they are listed
+as an updated module in the L</Modules and Pragmata> section.
 
-=head2 [CVE-2017-12814] C<$ENV{$key}> stack buffer overflow on Windows
+=back
 
-A possible stack buffer overflow in the C<%ENV> code on Windows has been fixed
-by removing the buffer completely since it was superfluous anyway.
-L<[perl #131665]|https://rt.perl.org/Public/Bug/Display.html?id=131665>
+[ List each other deprecation as a =head2 entry ]
 
 =head1 Performance Enhancements
 
+XXX Changes which enhance performance without changing behaviour go here.
+There may well be none in a stable release.
+
+[ List each enhancement as an =item entry ]
+
 =over 4
 
 =item *
 
-Slightly improved performance when parsing stash names.
-L<[perl #129990]|https://rt.perl.org/Public/Bug/Display.html?id=129990>
+XXX
 
 =back
 
 =head1 Modules and Pragmata
 
-=head2 Updated Modules and Pragmata
+XXX All changes to installed files in F<cpan/>, F<dist/>, F<ext/> and F<lib/>
+go here.  If Module::CoreList is updated, generate an initial draft of the
+following sections using F<Porting/corelist-perldelta.pl>.  A paragraph summary
+for important changes should then be added by hand.  In an ideal world,
+dual-life modules would have a F<Changes> file that could be cribbed.
+
+The list of new and updated modules is modified automatically as part of
+preparing a Perl release, so the only reason to manually add entries here is if
+you're summarising the important changes in the module update. (Also, if the
+manually-added details don't match the automatically-generated ones, the
+release manager will have to investigate the situation carefully.)
+
+[ Within each section, list entries as an =item entry ]
+
+=head2 New Modules and Pragmata
 
 =over 4
 
 =item *
 
-L<attributes> has been upgraded from version 0.3 to 0.31.
+XXX
 
-=item *
+=back
 
-L<File::Glob> has been upgraded from version 1.29 to 1.30.
+=head2 Updated Modules and Pragmata
+
+=over 4
 
 =item *
 
-L<I18N::Langinfo> has been upgraded from version 0.13 to 0.14.
-This fixes a bug in which the underlying locale was ignored for the
-C<RADIXCHAR> (always was returned as a dot, and the C<THOUSEP> (always
-empty).  Now the locale-appropriate values are returned.
+L<XXX> has been upgraded from version A.xx to B.yy.
 
-=item *
+=back
+
+=head2 Removed Modules and Pragmata
 
-L<Module::CoreList> has been upgraded from version 5.20170821 to 5.20170920.
+=over 4
 
 =item *
 
-L<sort> has been upgraded from version 2.02 to 2.03.
+XXX
 
-=item *
+=back
 
-L<Term::ReadLine> has been upgraded from version 1.16 to 1.17.
+=head1 Documentation
 
-=item *
+XXX Changes to files in F<pod/> go here.  Consider grouping entries by
+file and be sure to link to the appropriate page, e.g. L<perlfunc>.
 
-L<threads> has been upgraded from version 2.17 to 2.18.
+=head2 New Documentation
 
-=item *
+XXX Changes which create B<new> files in F<pod/> go here.
 
-L<VMS::Stdio> has been upgraded from version 2.41 to 2.42.
+=head3 L<XXX>
 
-=back
+XXX Description of the purpose of the new file here
 
-=head2 Removed Modules and Pragmata
+=head2 Changes to Existing Documentation
+
+We have attempted to update the documentation to reflect the changes
+listed in this document.  If you find any we have missed, send email
+to L<perlbug@perl.org|mailto:perlbug@perl.org>.
+
+XXX Changes which significantly change existing files in F<pod/> go here.
+However, any changes to F<pod/perldiag.pod> should go in the L</Diagnostics>
+section.
+
+Additionally, the following selected changes have been made:
+
+=head3 L<XXX>
 
 =over 4
 
 =item *
 
-The C<VMS::stdio> compatibility shim has been removed.
+XXX Description of the change here
 
 =back
 
@@ -140,178 +180,228 @@ 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 L<perldiag>.
 
-=head2 Changes to Existing Diagnostics
+XXX New or changed warnings emitted by the core's C<C> code go here.  Also
+include any changes in L<perldiag> that reconcile it to the C<C> code.
+
+=head2 New Diagnostics
+
+XXX Newly added diagnostic messages go under here, separated into New Errors
+and New Warnings
+
+=head3 New Errors
 
 =over 4
 
 =item *
 
-A false-positive warning that was issued when using a
-numerically-quantified sub-pattern in a recursive regex has been
-silenced. L<[perl #131868]|https://rt.perl.org/Public/Bug/Display.html?id=131868>
+XXX L<message|perldiag/"message">
 
 =back
 
-=head1 Testing
+=head3 New Warnings
 
-Tests were added and changed to reflect the other additions and changes
-in this release.
+=over 4
 
-=head1 Platform Support
+=item *
 
-=head2 Platform-Specific Notes
+XXX L<message|perldiag/"message">
+
+=back
+
+=head2 Changes to Existing Diagnostics
+
+XXX Changes (i.e. rewording) of diagnostic messages go here
 
 =over 4
 
-=item Darwin
+=item *
 
-Perl now correctly uses reentrant functions, like C<asctime_r>, on
-versions of Darwin that have support for them.
+XXX Describe change here
 
 =back
 
-=head1 Internal Changes
+=head1 Utility Changes
+
+XXX Changes to installed programs such as F<perlbug> and F<xsubpp> go here.
+Most of these are built within the directory F<utils>.
+
+[ List utility changes as a =head2 entry for each utility and =item
+entries for each change
+Use L<XXX> with program names to get proper documentation linking. ]
+
+=head2 L<XXX>
 
 =over 4
 
 =item *
 
-A new function, L<C<Perl_langinfo()>|perlapi/Perl_langinfo> has been
-added.  It is an (almost) drop-in replacement for the system
-C<nl_langinfo(3)>, but works on platforms that lack that; as well as
-being more thread-safe, and hiding some gotchas with locale handling
-from the caller.  Code that uses this, needn't use L<C<localeconv(3)>>
-(and be affected by the gotchas) to find the decimal point, thousands
-separator, or currency symbol.  See L<perlapi/Perl_langinfo>.
+XXX
 
-=item *
+=back
+
+=head1 Configuration and Compilation
+
+XXX Changes to F<Configure>, F<installperl>, F<installman>, and analogous tools
+go here.  Any other changes to the Perl build process should be listed here.
+However, any platform-specific changes should be listed in the
+L</Platform Support> section, instead.
 
-A new API function L<C<sv_rvunweaken()>|perlapi/sv_rvunweaken> has
-been added to complement L<C<sv_rvweaken()>|perlapi/sv_rvweaken>.
-The implementation was taken from L<Scalar::Util/unweaken>.
+[ List changes as an =item entry ].
+
+=over 4
 
 =item *
 
-A new flag, C<SORTf_UNSTABLE>, has been added. This will allow a
-future commit to make mergesort unstable when the user specifies ‘no
-sort stable’, since it has been decided that mergesort should remain
-stable by default.
+XXX
 
 =back
 
-=head1 Selected Bug Fixes
+=head1 Testing
+
+XXX Any significant changes to the testing of a freshly built perl should be
+listed here.  Changes which create B<new> files in F<t/> go here as do any
+large changes to the testing harness (e.g. when parallel testing was added).
+Changes to existing files in F<t/> aren't worth summarizing, although the bugs
+that they represent may be covered elsewhere.
+
+XXX If there were no significant test changes, say this:
+
+Tests were added and changed to reflect the other additions and changes
+in this release.
+
+XXX If instead there were significant changes, say this:
+
+Tests were added and changed to reflect the other additions and
+changes in this release.  Furthermore, these significant changes were
+made:
+
+[ List each test improvement as an =item entry ]
 
 =over 4
 
 =item *
 
-The internal stack usage checks introduced in 5.27.2 are now also done
-by the C<entersub> operator when calling XSUBs.  This means we can
-report which XSUB failed to allocate enough stack space.
-L<[perl #131975]|https://rt.perl.org/Public/Bug/Display.html?id=131975>
+XXX
 
-=item *
+=back
 
-Parsing a C<sub> definition could cause a use after free if the C<sub>
-keyword was followed by whitespace including newlines (and comments.)
-L<[perl #131836]|https://rt.perl.org/Public/Bug/Display.html?id=131836>
+=head1 Platform Support
 
-=item *
+XXX Any changes to platform support should be listed in the sections below.
 
-The tokenizer now correctly adjusts a parse pointer when skipping
-whitespace in a C< ${identifier} > construct.
-L<[perl #131949]|https://rt.perl.org/Public/Bug/Display.html?id=131949>
+[ Within the sections, list each platform as an =item entry with specific
+changes as paragraphs below it. ]
 
-=item *
+=head2 New Platforms
 
-Accesses to C<${^LAST_FH}> no longer assert after using any of a
-variety of I/O operations on a non-glob.
-L<[perl #128263]|https://rt.perl.org/Public/Bug/Display.html?id=128263>
+XXX List any platforms that this version of perl compiles on, that previous
+versions did not.  These will either be enabled by new files in the F<hints/>
+directories, or new subdirectories and F<README> files at the top level of the
+source tree.
 
-=item *
+=over 4
 
-The C<Copy()>, C<Move()>, C<Zero()> macros and their variants now
-assert if the pointers supplied are C<NULL>.  ISO C considers
-supplying NULL pointers to the functions these macros are built upon
-as undefined behaviour even when their count parameters are zero.
-Based on these assertions and the original bug report three macro
-calls were made conditional.
-L<[perl #131746]|https://rt.perl.org/Public/Bug/Display.html?id=131746>
-L<[perl #131892]|https://rt.perl.org/Public/Bug/Display.html?id=131892>
+=item XXX-some-platform
 
-=item *
+XXX
 
-The in-place sort optimisation now correctly strengthens weak
-references using the new L<C<sv_rvunweaken()>|perlapi/sv_rvunweaken>
-API function.
+=back
 
-=item *
+=head2 Discontinued Platforms
 
-Only the C<=> operator is permitted for defining defaults for
-parameters in subroutine signatures.  Previously other assignment
-operators, e.g. C<+=>, were also permitted.
-L<[perl #131777]|https://rt.perl.org/Public/Bug/Display.html?id=131777>
+XXX List any platforms that this version of perl no longer compiles on.
 
-=item *
+=over 4
 
-Package names are now always included in C<:prototype> warnings
-L<[perl #131833]|https://rt.perl.org/Public/Bug/Display.html?id=131833>
+=item XXX-some-platform
 
-=item *
+XXX
+
+=back
+
+=head2 Platform-Specific Notes
+
+XXX List any changes for specific platforms.  This could include configuration
+and compilation changes or changes in portability/compatibility.  However,
+changes within modules for platforms should generally be listed in the
+L</Modules and Pragmata> section.
+
+=over 4
 
-Creating a thread with no parameters no longer tries to C<Copy()> a
-null pointer. This fixes an assertion failure and allows threaded
-builds to work again.
+=item XXX-some-platform
+
+XXX
+
+=back
+
+=head1 Internal Changes
+
+XXX Changes which affect the interface available to C<XS> code go here.  Other
+significant internal changes for future core maintainers should be noted as
+well.
+
+[ List each change as an =item entry ]
+
+=over 4
 
 =item *
 
-The C<je_old_stack_hwm> field, previously only found in the C<jmpenv>
-structure on debugging builds, has been added to non-debug builds as
-well. This fixes an issue with some CPAN modules caused by the size of
-this structure varying between debugging and non-debugging builds.
-L<[perl #131942]|https://rt.perl.org/Public/Bug/Display.html?id=131942>
+XXX
+
+=back
+
+=head1 Selected Bug Fixes
+
+XXX Important bug fixes in the core language are summarized here.  Bug fixes in
+files in F<ext/> and F<lib/> are best summarized in L</Modules and Pragmata>.
+
+[ List each fix as an =item entry ]
+
+=over 4
 
 =item *
 
-The arguments to the C<ninstr()> macro are now correctly parenthesized.
+XXX
+
+=back
+
+=head1 Known Problems
+
+XXX Descriptions of platform agnostic bugs we know we can't fix go here.  Any
+tests that had to be C<TODO>ed for the release would be noted here.  Unfixed
+platform specific bugs also go here.
+
+[ List each fix as an =item entry ]
+
+=over 4
 
 =item *
 
-A NULL pointer dereference in the C<S_regmatch()> function has been
-fixed.
-L<[perl #132017]|https://rt.perl.org/Public/Bug/Display.html?id=132017>
+XXX
 
 =back
 
-=head1 Acknowledgements
+=head1 Errata From Previous Releases
 
-Perl 5.27.4 represents approximately 4 weeks of development since Perl 5.27.3
-and contains approximately 5,000 lines of changes across 140 files from 18
-authors.
+=over 4
 
-Excluding auto-generated files, documentation and release tools, there were
-approximately 3,300 lines of changes to 76 .pm, .t, .c and .h files.
+=item *
 
-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 5.27.4:
+XXX Add anything here that we forgot to add, or were mistaken about, in
+the perldelta of a previous release.
 
-Abigail, Chris 'BinGOs' Williams, Dagfinn Ilmari Mannsåker, David Mitchell,
-Dominic Hargreaves, Father Chrysostomos, H.Merijn Brand, James E Keenan, Jarkko
-Hietaniemi, John SJ Anderson, Karl Williamson, Lukas Mai, Matthew Horsfall,
-Neil Bowers, Nicolas R., Steve Hay, Tony Cook, Yves Orton.
+=back
 
-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.
+=head1 Obituary
+
+XXX If any significant core contributor has died, we've added a short obituary
+here.
+
+=head1 Acknowledgements
 
-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.
+XXX Generate this with:
 
-For a more complete list of all of Perl's historical contributors, please see
-the F<AUTHORS> file in the Perl source distribution.
+  perl Porting/acknowledgements.pl v5.25.5..HEAD
 
 =head1 Reporting Bugs
 
diff --git a/vms/descrip_mms.template b/vms/descrip_mms.template
index 829977e0d5..7e5325e90f 100644
--- a/vms/descrip_mms.template
+++ b/vms/descrip_mms.template
@@ -307,7 +307,7 @@ utils : $(utils1) $(utils2) $(utils3) $(utils4) $(utils5)
 extra.pods : miniperl
 	@ @extra_pods.com
 
-PERLDELTA_CURRENT = [.pod]perl5274delta.pod
+PERLDELTA_CURRENT = [.pod]perl5275delta.pod
 
 $(PERLDELTA_CURRENT) : [.pod]perldelta.pod
 	Copy/NoConfirm/Log $(MMS$SOURCE) $(PERLDELTA_CURRENT)
diff --git a/win32/GNUmakefile b/win32/GNUmakefile
index 16961e73d1..84e593996b 100644
--- a/win32/GNUmakefile
+++ b/win32/GNUmakefile
@@ -1635,7 +1635,7 @@ utils: $(HAVEMINIPERL) ..\utils\Makefile
 	copy ..\README.tw       ..\pod\perltw.pod
 	copy ..\README.vos      ..\pod\perlvos.pod
 	copy ..\README.win32    ..\pod\perlwin32.pod
-	copy ..\pod\perldelta.pod ..\pod\perl5274delta.pod
+	copy ..\pod\perldelta.pod ..\pod\perl5275delta.pod
 	$(MINIPERL) -I..\lib $(PL2BAT) $(UTILS)
 	$(MINIPERL) -I..\lib ..\autodoc.pl ..
 	$(MINIPERL) -I..\lib ..\pod\perlmodlib.PL -q ..
@@ -1732,7 +1732,7 @@ distclean: realclean
 	-if exist $(LIBDIR)\Win32API rmdir /s /q $(LIBDIR)\Win32API
 	-if exist $(LIBDIR)\XS rmdir /s /q $(LIBDIR)\XS
 	-cd $(PODDIR) && del /f *.html *.bat roffitall \
-	    perl5274delta.pod perlaix.pod perlamiga.pod perlandroid.pod \
+	    perl5275delta.pod perlaix.pod perlamiga.pod perlandroid.pod \
 	    perlapi.pod perlbs2000.pod perlce.pod perlcn.pod perlcygwin.pod \
 	    perldos.pod perlfreebsd.pod perlhaiku.pod perlhpux.pod \
 	    perlhurd.pod perlintern.pod perlirix.pod perljp.pod perlko.pod \
diff --git a/win32/Makefile b/win32/Makefile
index 3998517c5f..6c7a86e252 100644
--- a/win32/Makefile
+++ b/win32/Makefile
@@ -1270,7 +1270,7 @@ utils: $(PERLEXE) ..\utils\Makefile
 	copy ..\README.tw       ..\pod\perltw.pod
 	copy ..\README.vos      ..\pod\perlvos.pod
 	copy ..\README.win32    ..\pod\perlwin32.pod
-	copy ..\pod\perldelta.pod ..\pod\perl5274delta.pod
+	copy ..\pod\perldelta.pod ..\pod\perl5275delta.pod
 	cd ..\win32
 	$(PERLEXE) $(PL2BAT) $(UTILS)
 	$(MINIPERL) -I..\lib ..\autodoc.pl ..
@@ -1369,7 +1369,7 @@ distclean: realclean
 	-if exist $(LIBDIR)\Win32API rmdir /s /q $(LIBDIR)\Win32API
 	-if exist $(LIBDIR)\XS rmdir /s /q $(LIBDIR)\XS
 	-cd $(PODDIR) && del /f *.html *.bat roffitall \
-	    perl5274delta.pod perlaix.pod perlamiga.pod perlandroid.pod \
+	    perl5275delta.pod perlaix.pod perlamiga.pod perlandroid.pod \
 	    perlapi.pod perlbs2000.pod perlce.pod perlcn.pod perlcygwin.pod \
 	    perldos.pod perlfreebsd.pod perlhaiku.pod perlhpux.pod \
 	    perlhurd.pod perlintern.pod perlirix.pod perljp.pod perlko.pod \
diff --git a/win32/makefile.mk b/win32/makefile.mk
index b13b5975cb..200134ac31 100644
--- a/win32/makefile.mk
+++ b/win32/makefile.mk
@@ -1581,7 +1581,7 @@ utils: $(HAVEMINIPERL) ..\utils\Makefile
 	copy ..\README.tw       ..\pod\perltw.pod
 	copy ..\README.vos      ..\pod\perlvos.pod
 	copy ..\README.win32    ..\pod\perlwin32.pod
-	copy ..\pod\perldelta.pod ..\pod\perl5274delta.pod
+	copy ..\pod\perldelta.pod ..\pod\perl5275delta.pod
 	$(MINIPERL) -I..\lib $(PL2BAT) $(UTILS)
 	$(MINIPERL) -I..\lib ..\autodoc.pl ..
 	$(MINIPERL) -I..\lib ..\pod\perlmodlib.PL -q ..
@@ -1679,7 +1679,7 @@ distclean: realclean
 	-if exist $(LIBDIR)\Win32API rmdir /s /q $(LIBDIR)\Win32API
 	-if exist $(LIBDIR)\XS rmdir /s /q $(LIBDIR)\XS
 	-cd $(PODDIR) && del /f *.html *.bat roffitall \
-	    perl5274delta.pod perlaix.pod perlamiga.pod perlandroid.pod \
+	    perl5275delta.pod perlaix.pod perlamiga.pod perlandroid.pod \
 	    perlapi.pod perlbs2000.pod perlce.pod perlcn.pod perlcygwin.pod \
 	    perldos.pod perlfreebsd.pod perlhaiku.pod perlhpux.pod \
 	    perlhurd.pod perlintern.pod perlirix.pod perljp.pod perlko.pod \
diff --git a/win32/pod.mak b/win32/pod.mak
index bd2fb621d1..84443c4619 100644
--- a/win32/pod.mak
+++ b/win32/pod.mak
@@ -54,6 +54,7 @@ POD = perl.pod	\
 	perl5272delta.pod	\
 	perl5273delta.pod	\
 	perl5274delta.pod	\
+	perl5275delta.pod	\
 	perl561delta.pod	\
 	perl56delta.pod	\
 	perl581delta.pod	\
@@ -203,6 +204,7 @@ MAN = perl.man	\
 	perl5272delta.man	\
 	perl5273delta.man	\
 	perl5274delta.man	\
+	perl5275delta.man	\
 	perl561delta.man	\
 	perl56delta.man	\
 	perl581delta.man	\
@@ -351,6 +353,7 @@ HTML = perl.html	\
 	perl5272delta.html	\
 	perl5273delta.html	\
 	perl5274delta.html	\
+	perl5275delta.html	\
 	perl561delta.html	\
 	perl56delta.html	\
 	perl581delta.html	\
@@ -500,6 +503,7 @@ TEX = perl.tex	\
 	perl5272delta.tex	\
 	perl5273delta.tex	\
 	perl5274delta.tex	\
+	perl5275delta.tex	\
 	perl561delta.tex	\
 	perl56delta.tex	\
 	perl581delta.tex	\