=encoding utf8
-=for comment
-This has been completed up to 0aae26c14, except for:
-803e389 rurban CYG17 utf8 paths
-d9298c1 rurban mymalloc isn't thread safe
-
=head1 NAME
-[ 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 v5.15.8
+perldelta - what is new for perl v5.16.0
=head1 DESCRIPTION
-This document describes differences between the 5.15.7 release and
-the 5.15.8 release.
+This document describes differences between the 5.14.0 release and
+the 5.16.0 release.
-If you are upgrading from an earlier release such as 5.15.6, first read
-L<perl5157delta>, which describes differences between 5.15.6 and
-5.15.7.
+If you are upgrading from an earlier release such as 5.12.0, first read
+L<perl5140delta>, which describes differences between 5.12.0 and
+5.14.0.
=head1 Notice
-XXX Any important notices here
+As described in L<perlpolicy>, the release of Perl 5.16.0 marks the
+official end of support for Perl 5.12. Users of Perl 5.12 or earlier
+should consider upgrading to a more recent release of Perl.
=head1 Core Enhancements
-XXX New core language features go here. Summarise user-visible core language
-enhancements. Particularly prominent performance optimisations could go
-here, but most should go in the L</Performance Enhancements> section.
+=head2 C<use I<VERSION>>
-[ List each enhancement as a =head2 entry ]
+As of this release, version declarations like C<use v5.16> now disable
+all features before enabling the new feature bundle. This means that
+the following holds true:
-=head2 Improved ability to mix locales and Unicode, including UTF-8 locales
+ use 5.016;
+ # only 5.16 features enabled here
+ use 5.014;
+ # only 5.14 features enabled here (not 5.16)
-An optional parameter has been added to C<use locale>
+C<use v5.12> and higher continue to enable strict, but explicit C<use
+strict> and C<no strict> now override the version declaration, even
+when they come first:
- use locale ':not_characters';
+ no strict;
+ use 5.012;
+ # no strict here
-which tells Perl to use all but the C<LC_CTYPE> and C<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 C<:locale> layer to the L<open> pragma can
-be used to interface with the file system, and there are CPAN modules
-available for ARGV and environment variable conversions.
+There is a new ":default" feature bundle that represents the set of
+features enabled before any version declaration or C<use feature> has
+been seen. Version declarations below 5.10 now enable the ":default"
+feature set. This does not actually change the behaviour of C<use
+v5.8>, because features added to the ":default" set are those that were
+traditionally enabled by default, before they could be turned off.
-Full details are in L<perllocale>.
+C<< no feature >> now resets to the default feature set. To disable all
+features (which is likely to be a pretty special-purpose request, since
+it presumably won't match any named set of semantics) you can now
+write C<< no feature ':all' >>.
-=head2 New function C<fc> and corresponding escape sequence C<\F> for Unicode foldcase
+C<$[> is now disabled under C<use v5.16>. It is part of the default
+feature set and can be turned on or off explicitly with C<use feature
+'array_base'>.
-Unicode foldcase is an extension to lowercase that gives better results
-when comparing two strings case-insensitively. It has long been used
-internally in regular expression C</i> matching. Now it is available
-explicitly through the new C<fc> function call (enabled by
-S<C<"use feature 'fc'">>, or C<use v5.16>, or explicitly callable via
-C<CORE::fc>) or through the new C<\F> sequence in double-quotish
-strings.
+=head2 C<__SUB__>
-Full details are in L<perlfunc/fc>.
+The new C<__SUB__> token, available under the C<current_sub> feature
+(see L<feature>) or C<use v5.16>, returns a reference to the current
+subroutine, making it easier to write recursive closures.
-=head2 C<_> in subroutine prototypes
+=head2 New and Improved Built-ins
-The C<_> character in subroutine prototypes is now allowed before C<@> or
-C<%>.
+=head3 More consistent C<eval>
+
+The C<eval> operator sometimes treats a string argument as a sequence of
+characters and sometimes as a sequence of bytes, depending on the
+internal encoding. The internal encoding is not supposed to make any
+difference, but there is code that relies on this inconsistency.
+
+The new C<unicode_eval> and C<evalbytes> features (enabled under C<use
+5.16.0>) resolve this. The C<unicode_eval> feature causes C<eval
+$string> to treat the string always as Unicode. The C<evalbytes>
+features provides a function, itself called C<evalbytes>, which
+evaluates its argument always as a string of bytes.
+
+These features also fix oddities with source filters leaking to outer
+dynamic scopes.
+
+See L<feature> for more detail.
+
+=head3 C<substr> lvalue revamp
+
+=for comment Does this belong here, or under Incomptable Changes?
+
+When C<substr> is called in lvalue or potential lvalue context with two
+or three arguments, a special lvalue scalar is returned that modifies
+the original string (the first argument) when assigned to.
+
+Previously, the offsets (the second and third arguments) passed to
+C<substr> would be converted immediately to match the string, negative
+offsets being translated to positive and offsets beyond the end of the
+string being truncated.
+
+Now, the offsets are recorded without modification in the special
+lvalue scalar that is returned, and the original string is not even
+looked at by C<substr> itself, but only when the returned lvalue is
+read or modified.
+
+These changes result in an incompatible change:
-=head1 Supports (I<almost>) Unicode 6.1
+If the original string changes length after the call to C<substr> but
+before assignment to its return value, negative offsets will remember
+their position from the end of the string, affecting code like this:
+
+ my $string = "string";
+ my $lvalue = \substr $string, -4, 2;
+ print $lvalue, "\n"; # prints "ri"
+ $string = "bailing twine";
+ print $lvalue, "\n"; # prints "wi"; used to print "il"
+
+The same thing happens with an omitted third argument. The returned
+lvalue will always extend to the end of the string, even if the string
+becomes longer.
+
+Since this change also allowed many bugs to be fixed (see
+L</The C<substr> operator>), and since the behaviour
+of negative offsets has never been specified, so the
+change was deemed acceptable.
+
+=head3 Return value of C<tied>
+
+The value returned by C<tied> on a tied variable is now the actual
+scalar that holds the object to which the variable is tied. This
+allows ties to be weakened with C<Scalar::Util::weaken(tied
+$tied_variable)>.
+
+=head2 Unicode Support
+
+=head3 Supports (I<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
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
+these, along with the previously existing ones, are all cross-indexed in
L<perluniprops>.
-The return value of C<charnames::viacode> is affected by other changes.
-One of these is that the preferred name (which is what C<viacode>
-returns) for the character at U+2118 has been changed from SCRIPT CAPITAL P
-to WEIERSTRASS ELLIPTIC FUNCTION. But most of these changes are the
+The return value of C<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+000D CARRIAGE RETURN (CR) CARRIAGE RETURN
+ 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
+ U+2118 SCRIPT CAPITAL P WEIERSTRASS ELLIPTIC FUNCTION
+
+Perl will accept any of these names as input, but
+C<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
+Japanese cell phones to be "BELL", which conflicts with the longstanding
+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
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. This means that all the names that Perl had previously
-deprecated (except BELL) are no longer deprecated, such as FILE
-SEPARATOR. Also, the names for four rarely used characters are subtly
-different (a hyphen instead of a space) than before:
-
- Code point Old Name New Name
- 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 either name as input, but C<charnames::viacode> now
-returns the new name.
-
-Additional name abbreviations are accepted:
+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;
More details on this version of Unicode are provided in
L<http://www.unicode.org/versions/Unicode6.1.0/>.
-=head1 Security
-
-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.
+=head3 C<use charnames> is no longer needed for C<\N{I<name>}>
-[ List each security issue as a =head2 entry ]
+When C<\N{I<name>}> is encountered, the C<charnames> module is now
+automatically loaded when needed as if the C<:full> and C<:short>
+options had been specified. See L<charnames> for more information.
-=head1 Incompatible Changes
+=head3 C<\N{...}> can now have Unicode loose name matching
-XXX For a release on a stable branch, this section aspires to be:
+This is described in the C<charnames> item in
+L</Updated Modules and Pragmata> below.
- 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.
+=head3 Unicode Symbol Names
-[ List each incompatible change as a =head2 entry ]
+Perl now has proper support for Unicode in symbol names. It used to be
+that C<*{$foo}> would ignore the internal UTF8 flag and use the bytes of
+the underlying representation to look up the symbol. That meant that
+C<*{"\x{100}"}> and C<*{"\xc4\x80"}> would return the same thing. All
+these parts of Perl have been fixed to account for Unicode:
-=head2 Special blocks called in void context
+=over
-Special blocks (C<BEGIN>, C<CHECK>, C<INIT>, C<UNITCHECK>, C<END>) are now
-called in void context. This avoids wasteful copying of the result of the
-last statement [perl #108794].
+=item *
-=head2 The C<overloading> pragma and regexp objects
+Method names (including those passed to C<use overload>)
-With C<no overloading>, regular expression objects returned by C<qr//> are
-now stringified as "Regexp=REGEXP(0xbe600d)" instead of the regular
-expression itself [perl #108780].
+=item *
-=head2 Two XS typemap Entries removed
+Typeglob names (including names of variables, subroutines and filehandles)
-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 L<perlxstypemap>.
+=item *
-=head2 Unicode 6.1 has incompatibilities with Unicode 6.0
+Package names
-These are detailed in L</Supports (almost) Unicode 6.1> above.
+=item *
-=head2 Changed returns for some properties in C<Unicode::UCD::prop_invmap()>
+C<goto>
-The return values for C<prop_invmap> have been changed for some
-properties to make the returned lists significantly smaller. This
-allows those lists to be searched faster.
+=item *
-This function was introduced earlier in the v5.15 series of releases,
-and the API will not be considered stable until v5.16.
+Symbolic dereferencing
-See L<Unicode::UCD/prop_invmap()> for details on the new interface.
+=item *
-=head1 Deprecations
+Second argument to C<bless()> and C<tie()>
-XXX Any deprecated features, syntax, modules etc. should be listed here.
-In particular, deprecated modules should be listed here even if they are
-listed as an updated module in the L</Modules and Pragmata> section.
+=item *
-[ List each deprecation as a =head2 entry ]
+Return value of C<ref()>
-=head1 Performance Enhancements
+=item *
-XXX Changes which enhance performance without changing behaviour go here. There
-may well be none in a stable release.
+Subroutine prototypes
-[ List each enhancement as a =item entry ]
+=item *
-=over 4
+Attributes
=item *
-XXX
+Various warnings and error messages that mention variable names or values,
+methods, etc.
=back
-=head1 Modules and Pragmata
+In addition, a parsing bug has been fixed that prevented C<*{é}> from
+implicitly quoting the name, but instead interpreted it as C<*{+é}>, which
+would cause a strict violation.
-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>, which prints stub
-entries to STDOUT. Results can be pasted in place of the '=head2' entries
-below. 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.
+C<*{"*a::b"}> automatically strips off the * if it is followed by an ASCII
+letter. That has been extended to all Unicode identifier characters.
-[ Within each section, list entries as a =item entry ]
+One-character non-ASCII non-punctuation variables (like C<$é>) are now
+subject to "Used only once" warnings. They used to be exempt, as they
+was treated as punctuation variables.
-=head2 New Modules and Pragmata
+Also, single-character Unicode punctuation variables (like C<$‰>) are now
+supported [perl #69032].
-=over 4
+=head3 Improved ability to mix locales and Unicode, including UTF-8 locales
-=item *
+An optional parameter has been added to C<use locale>
-The C<mmap> PerlIO layer is no longer implemented by perl itself, but has
-been moved out into the new L<PerlIO::mmap> module.
+ use locale ':not_characters';
-=back
+which tells Perl to use all but the C<LC_CTYPE> and C<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 C<:locale> layer to the L<open> pragma can
+be used to interface with the file system, and there are CPAN modules
+available for ARGV and environment variable conversions.
-=head2 Updated Modules and Pragmata
+Full details are in L<perllocale>.
-=over 4
+=head3 New function C<fc> and corresponding escape sequence C<\F> for Unicode foldcase
-=item *
+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 C</i> matching. Now it is available
+explicitly through the new C<fc> function call (enabled by
+S<C<"use feature 'fc'">>, or C<use v5.16>, or explicitly callable via
+C<CORE::fc>) or through the new C<\F> sequence in double-quotish
+strings.
-L<arybase> has been upgraded from version 0.03 to version 0.04.
+Full details are in L<perlfunc/fc>.
-List slices no longer modify items on the stack belonging to outer lists
-[perl #109570].
+=head3 The Unicode C<Script_Extensions> property is now supported.
-=item *
+New in Unicode 6.0, this is an improved C<Script> property. Details
+are in L<perlunicode/Scripts>.
-L<B> has been upgraded from version 1.33 to version 1.34.
+=head2 XS Changes
-C<B::COP> now has a C<stashflags> method, corresponding to a new internal
-field added in 5.15.4 [perl #108860].
+=head3 Improved typemaps for Some Builtin Types
-=item *
+Most XS authors will be aware that there is a longstanding bug in the
+OUTPUT typemap for T_AVREF (C<AV*>), T_HVREF (C<HV*>), T_CVREF (C<CV*>),
+and T_SVREF (C<SVREF> or C<\$foo>) that requires manually decrementing
+the reference count of the return value instead of the typemap taking
+care of this. For backwards-compatibility, this cannot be changed in the
+default typemaps. But we now provide additional typemaps
+C<T_AVREF_REFCOUNT_FIXED>, etc. that do not exhibit this bug. Using
+them in your extension is as simple as having one line in your
+C<TYPEMAP> section:
-L<Carp> has been upgraded from version 1.24 to version 1.25.
+ HV* T_HVREF_REFCOUNT_FIXED
-It now puts a dot after the file and line number, just like errors from
-C<die> [perl #106538].
+=head3 C<is_utf8_char()>
-=item *
+The XS-callable function C<is_utf8_char()>, when presented with
+malformed UTF-8 input, can read up to 12 bytes beyond the end of the
+string. This cannot be fixed without changing its API. It is not
+called from CPAN. The documentation now describes how to use it
+safely.
-L<Compress::Raw::Bzip2> has been upgraded from version 2.045 to version 2.048.
+=head3 Added C<is_utf8_char_buf()>
-=item *
+This function is designed to replace the deprecated L</is_utf8_char()>
+function. It includes an extra parameter to make sure it doesn't read
+past the end of the input buffer.
-L<Compress::Raw::Zlib> has been upgraded from version 2.045 to version 2.048.
+=head3 Other C<is_utf8_foo()> functions, as well as C<utf8_to_foo()>, etc.
-=item *
+Most of the other XS-callable functions that take UTF-8 encoded input
+implicitly assume that the UTF-8 is valid (not malformed) in regards to
+buffer length. Do not do things such as change a character's case or
+see if it is alphanumeric without first being sure that it is valid
+UTF-8. This can be safely done for a whole string by using one of the
+functions C<is_utf8_string()>, C<is_utf8_string_loc()>, and
+C<is_utf8_string_loclen()>.
-L<Compress::Zlib> has been upgraded from version 2.046 to version 2.048.
+=head3 New Pad API
-=item *
+Many new functions have been added to the API for manipulating lexical
+pads. See L<perlapi/Pad Data Structures> for more information.
-L<CPAN::Meta> has been upgraded from version 2.113640 to version 2.120351.
+=head2 Changes to Special Variables
-Work around a memory leak bug involving version objects in boolean context.
+=head3 C<$$> can be assigned to
-=item *
+C<$$> was made read-only in Perl 5.8.0. But only sometimes: C<local $$>
+would make it writable again. Some CPAN modules were using C<local $$> or
+XS code to bypass the read-only check, so there is no reason to keep C<$$>
+read-only. (This change also allowed a bug to be fixed while maintaining
+backward compatibility.)
-L<CPAN::Meta::YAML> has been upgraded from version 0.005 to version 0.007.
+=head3 C<$^X> converted to an absolute path on FreeBSD, OS X and Solaris
-=item *
+C<$^X> is now converted to an absolute path on OS X, FreeBSD (without
+needing F</proc> mounted) and Solaris 10 and 11. This augments the
+previous approach of using F</proc> on Linux, FreeBSD and NetBSD
+(in all cases, where mounted).
-L<DB_File> has been upgraded from version 1.824 to version 1.826.
+This makes relocatable perl installations more useful on these platforms.
+(See "Relocatable @INC" in F<INSTALL>)
-=item *
+=head2 Debugger Changes
-L<diagnostics> has been upgraded from version 1.27 to version 1.28.
+=head3 Features inside the debugger
-When searching for F<perldiag.pod>, it no longer uses paths that were only
-relevant on Perl 5.004 and earlier.
+The current Perl's L<feature> bundle is now enabled for commands entered
+in the interactive debugger.
-=item *
+=head3 New option for the debugger's B<t> command
-L<ExtUtils::ParseXS> has been upgraded from version 3.12 to version 3.15.
+The B<t> command in the debugger, which toggles tracing mode, now
+accepts a numeric argument that determines how many levels of subroutine
+calls to trace.
-The new version comes with important tools for sharing typemaps between
-different CPAN distributions.
+=head3 C<enable> and C<disable>
-=item *
+The debugger now has C<disable> and C<enable> commands for disabling
+existing breakpoints and re-enabling them. See L<perldebug>.
-L<File::Copy> has been upgraded from version 2.21 to version 2.23.
+=head3 Breakpoints with file names
-It no longer emits warnings when copying files with newlines in their names
-[perl #109104].
+The debugger's "b" command for setting breakpoints now allows a line
+number to be prefixed with a file name. See
+L<perldebug/"b [file]:[line] [condition]">.
-=item *
+=head2 The C<CORE> Namespace
-L<IPC::Cmd> has been upgraded from version 0.72 to version 0.76.
+=head3 The C<CORE::> prefix
-=item *
+The C<CORE::> prefix can now be used on keywords enabled by
+L<feature.pm|feature>, even outside the scope of C<use feature>.
-L<Math::Complex> has been upgraded from version 1.58 to version 1.59.
+=head3 Subroutines in the C<CORE> namespace
-This avoids a new core warning.
+Many Perl keywords are now available as subroutines in the CORE namespace.
+This allows them to be aliased:
-=item *
+ BEGIN { *entangle = \&CORE::tie }
+ entangle $variable, $package, @args;
-L<Module::Metadata> has been upgraded from version 1.000007 to version 1.000008.
+And for prototypes to be bypassed:
-Adds C<provides> method to generate a CPAN META provides data structure
-correctly; use of C<package_versions_from_directory> is discouraged.
+ sub mytie(\[%$*@]$@) {
+ my ($ref, $pack, @args) = @_;
+ ... do something ...
+ goto &CORE::tie;
+ }
-=item *
+Some of these cannot be called through references or via C<&foo> syntax,
+but must be called as barewords.
-L<Parse::CPAN::Meta> has been upgraded from version 1.4401 to version 1.4402.
+See L<CORE> for details.
-=item *
+=head2 Other Changes
-L<Pod::Parser> has been upgraded from version 1.37 to version 1.51.
+=head3 Anonymous handles
-=item *
+Automatically generated file handles are now named __ANONIO__ when the
+variable name cannot be determined, rather than $__ANONIO__.
-L<Term::ReadLine> has been upgraded from version 1.07 to version 1.08.
+=head3 Autoloaded sort Subroutines
-Its C<tkRunning> method now supports L<AnyEvent> event loops, and not just
-L<Tk>. A more general mechanism has been proposed, so this may be reverted
-before Perl 5.16 [perl #108470].
+Custom sort subroutines can now be autoloaded [perl #30661]:
-=item *
+ sub AUTOLOAD { ... }
+ @sorted = sort foo @list; # uses AUTOLOAD
-L<Time::HiRes> has been upgraded from version 1.9724 to version 1.9725.
+=head3 C<continue> no longer requires the "switch" feature
-C<Time::HiRes::stat()> no longer corrupts the Perl stack.
+The C<continue> keyword has two meanings. It can introduce a C<continue>
+block after a loop, or it can exit the current C<when> block. Up till now,
+the latter meaning was only valid with the "switch" feature enabled, and
+was a syntax error otherwise. Since the main purpose of feature.pm is to
+avoid conflicts with user-defined subroutines, there is no reason for
+C<continue> to depend on it.
-=item *
+=head3 DTrace probes for interpreter phase change
-L<Unicode::UCD> has been upgraded from version 0.39 to 0.40.
+The C<phase-change> probes will fire when the interpreter's phase
+changes, which tracks the C<${^GLOBAL_PHASE}> variable. C<arg0> is
+the new phase name; C<arg1> is the old one. This is useful mostly
+for limiting your instrumentation to one or more of: compile time,
+run time, destruct time.
-The only change is to fix a formatting error in the Pod.
+=head3 C<__FILE__()> Syntax
-=item *
+The C<__FILE__>, C<__LINE__> and C<__PACKAGE__> tokens can now be written
+with an empty pair of parentheses after them. This makes them parse the
+same way as C<time>, C<fork> and other built-in functions.
-L<Version::Requirements> has been upgraded from version 0.101021 to version 0.101022.
+=head3 The C<\$> prototype accepts any scalar lvalue
-=back
+The C<\$> and C<\[$]> subroutine prototypes now accept any scalar lvalue
+argument. Previously they only accepted scalars beginning with C<$> and
+hash and array elements. This change makes them consistent with the way
+the built-in C<read> and C<recv> functions (among others) parse their
+arguments. This means that one can override the built-in functions with
+custom subroutines that parse their arguments the same way.
-=head2 Removed Modules and Pragmata
+=head3 C<_> in subroutine prototypes
-=over 4
+The C<_> character in subroutine prototypes is now allowed before C<@> or
+C<%>.
-=item *
+=head1 Security
-XXX
+=head2 Use C<is_utf8_char_buf()> and not C<is_utf8_char()>
-=back
+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
+L<is_utf8_char_buf()|/Added is_utf8_char_buf()>.
-=head1 Documentation
+=head2 Malformed UTF-8 input could cause attempts to read beyond the end of the buffer
-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>.
+Two new XS-accessible functions, C<utf8_to_uvchr_buf()> and
+C<utf8_to_uvuni_buf()> are now available to prevent this, and the Perl
+core has been converted to use them.
+See L</Internal Changes>.
-=head2 New Documentation
+=head2 C<File::Glob::bsd_glob()> memory error with GLOB_ALTDIRFUNC (CVE-2011-2728).
-XXX Changes which create B<new> files in F<pod/> go here.
+Calling C<File::Glob::bsd_glob> with the unsupported flag
+GLOB_ALTDIRFUNC would cause an access violation / segfault. A Perl
+program that accepts a flags value from an external source could expose
+itself to denial of service or arbitrary code execution attacks. There
+are no known exploits in the wild. The problem has been corrected by
+explicitly disabling all unsupported flags and setting unused function
+pointers to null. Bug reported by Clément Lecigne.
-=head3 L<perlxstypemap>
+=head2 Privileges are now set correctly when assigning to C<$(>
-The new manual describes the XS typemapping mechanism in unprecedented
-detail and combines new documentation with information extracted from
-L<perlxs> and the previously unofficial list of all core typemaps.
+A hypothetical bug (probably non-exploitable in practice) due to the
+incorrect setting of the effective group ID while setting C<$(> has been
+fixed. The bug would only have affected systems that have C<setresgid()>
+but not C<setregid()>, but no such systems are known of.
-=head3 L<XXX>
+=head1 Deprecations
-XXX Description of the purpose of the new file here
+=head2 Don't read the Unicode data base files in F<lib/unicore>
-=head2 Changes to Existing Documentation
+It is now deprecated to directly read the Unicode data base files.
+These are stored in the F<lib/unicore> directory. Instead, you should
+use the new functions in L<Unicode::UCD>. These provide a stable API,
+and give complete information.
-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.
+Perl may at some point in the future change or remove the files. The
+file most likely for applications to have used is
+F<lib/unicore/ToDigit.pl>. L<Unicode::UCD/prop_invmap()> can be used to
+get at its data instead.
-=head3 L<XXX>
+=head2 XS functions C<is_utf8_char()>, C<utf8_to_uvchr()> and
+C<utf8_to_uvuni()>
-=over 4
+This function is deprecated because it could read beyond the end of the
+input string. Use the new L<is_utf8_char_buf()|/Added is_utf8_char_buf()>,
+C<utf8_to_uvchr_buf()> and C<utf8_to_uvuni_buf()> instead.
-=item *
+=head1 Future Deprecations
-XXX Description of the change here
+This section serves as a notice of features that are I<likely> to be
+removed or L<deprecated|perlpolicy/deprecated> in the next release of
+perl (5.18.0). If your code depends on these features, you should
+contact the Perl 5 Porters via the L<mailing
+list|http://lists.perl.org/list/perl5-porters.html> or L<perlbug> to
+explain your use case and inform the deprecation process.
-=back
+=head2 Core Modules
-=head1 Diagnostics
+These modules may be marked as deprecated I<from the core>. This only
+means that they will no longer be installed by default with the core
+distribution, but will remain available on the CPAN.
-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>.
+=over
-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.
+=item *
-[ Within each section, list entries as a =item entry that links to perldiag,
- e.g.
+CPANPLUS
- =item *
+=item *
- L<Invalid version object|perldiag/"Invalid version object">
-]
+Filter::Simple
-=head2 New Diagnostics
+=item *
-XXX Newly added diagnostic messages go here
+PerlIO::mmap
-=head3 New Errors
+=item *
-=over 4
+Pod::Parser, Pod::LaTeX
=item *
-XXX L<message|perldiag/"message">
-
-=back
+SelfLoader
-=head3 New Warnings
+=item *
-=over 4
+Text::Soundex
=item *
-XXX L<message|perldiag/"message">
+Thread.pm
=back
-=head2 Changes to Existing Diagnostics
+=head2 Platforms with no supporting programmers:
-XXX Changes (i.e. rewording) of diagnostic messages go here
+These platforms will probably have their
+special build support removed during the
+5.17.0 development series.
-=over 4
+=over
=item *
-XXX Describe change here
+BeOS
-=back
+=item *
-=head1 Utility Changes
+djgpp
-XXX Changes to installed programs such as F<perlbug> and F<xsubpp> go
-here. Most of these are built within the directories F<utils> and F<x2p>.
+=item *
-[ List utility changes as a =head3 entry for each utility and =item
-entries for each change
-Use L<XXX> with program names to get proper documentation linking. ]
+dgux
-=head3 L<XXX>
+=item *
-=over 4
+EPOC
=item *
-XXX
-
-=back
+MPE/iX
-=head1 Configuration and Compilation
+=item *
-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.
+Rhapsody
-[ List changes as a =item entry ].
+=item *
-=over 4
+UTS
=item *
-XXX
+VM/ESA
=back
-=head1 Testing
+=head2 Other Future Deprecations
-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 summarising, although the bugs
-that they represent may be covered elsewhere.
+=over
-[ List each test improvement as a =item entry ]
+=item *
-=over 4
+Swapping of $< and $>
+
+For more information about this future deprecation, see L<the relevant RT
+ticket|https://rt.perl.org/rt3/Ticket/Display.html?id=96212>.
=item *
-XXX
+sfio, stdio
+
+Perl supports being built without PerlIO proper, using a stdio or sfio
+wrapper instead. A perl build like this will not support IO layers and
+thus Unicode IO, making it rather handicapped.
+
+PerlIO supports a C<stdio> layer if stdio use is desired, and similarly a
+sfio layer could be produced.
=item *
-The test suite for typemaps has been extended to cover a larger fraction of
-the core typemaps.
+Unescaped literal C<< "{" >> in regular expressions.
+
+It is planned starting in v5.20 to require a literal C<"{"> to be
+escaped by, for example, preceding it with a backslash. In v5.18, a
+deprecated warning message will be emitted for all such uses. Note that
+this only affects patterns which are to match a literal C<"{">. Other
+uses of this character, such as part of a quantifier or sequence like in
+the ones below are completely unaffected:
+
+ /foo{3,5}/
+ /\p{Alphabetic}/
+ /\N{DIGIT ZERO}
+
+The removal of this will allow extensions to pattern syntax, and better
+error checking of existing syntax. See L<perlre/Quantifiers> for an
+example.
=back
-=head1 Platform Support
+=head1 Incompatible Changes
+
+=head2 Special blocks called in void context
-XXX Any changes to platform support should be listed in the sections below.
+Special blocks (C<BEGIN>, C<CHECK>, C<INIT>, C<UNITCHECK>, C<END>) are now
+called in void context. This avoids wasteful copying of the result of the
+last statement [perl #108794].
-[ Within the sections, list each platform as a =item entry with specific
-changes as paragraphs below it. ]
+=head2 The C<overloading> pragma and regexp objects
-=head2 New Platforms
+With C<no overloading>, regular expression objects returned by C<qr//> are
+now stringified as "Regexp=REGEXP(0xbe600d)" instead of the regular
+expression itself [perl #108780].
-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.
+=head2 Two XS typemap Entries removed
-=over 4
+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 L<perlxstypemap>.
-=item XXX-some-platform
+=head2 Unicode 6.1 has incompatibilities with Unicode 6.0
-XXX
+These are detailed in L</Supports (almost) Unicode 6.1> above.
+You can compile this version of Perl to use Unicode 6.0. See
+L<perlunicode/Hacking Perl to work on earlier Unicode versions (for very serious hackers only)>.
-=back
+=head2 Borland compiler
-=head2 Discontinued Platforms
+All support for the Borland compiler has been dropped. The code had not
+worked for a long time anyway.
-XXX List any platforms that this version of perl no longer compiles on.
+=head2 Certain deprecated Unicode properties are no longer supported by default
-=over 4
+Perl should never have exposed certain Unicode properties that are used
+by Unicode internally and not meant to be publicly available. Use of
+these has generated deprecated warning messages since Perl 5.12. The
+removed properties are Other_Alphabetic,
+Other_Default_Ignorable_Code_Point, Other_Grapheme_Extend,
+Other_ID_Continue, Other_ID_Start, Other_Lowercase, Other_Math, and
+Other_Uppercase.
-=item XXX-some-platform
+Perl may be recompiled to include any or all of them; instructions are
+given in
+L<perluniprops/Unicode character properties that are NOT accepted by Perl>.
-XXX
+=head2 Dereferencing IO thingies as typeglobs
-=back
+The C<*{...}> operator, when passed a reference to an IO thingy (as in
+C<*{*STDIN{IO}}>), creates a new typeglob containing just that IO object.
+Previously, it would stringify as an empty string, but some operators would
+treat it as undefined, producing an "uninitialized" warning.
+Now it stringifies as __ANONIO__ [perl #96326].
-=head2 Platform-Specific Notes
+=head2 User-defined case-changing operations
-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.
+This feature was deprecated in Perl 5.14, and has now been removed.
+The CPAN module L<Unicode::Casing> provides better functionality without
+the drawbacks that this feature had, as are detailed in the 5.14
+documentation:
+L<http://perldoc.perl.org/5.14.0/perlunicode.html#User-Defined-Case-Mappings-%28for-serious-hackers-only%29>
-=over 4
+=head2 XSUBs are now 'static'
-=item XXX-some-platform
+XSUB C functions are now 'static', that is, they are not visible from
+outside the compilation unit. Users can use the new C<XS_EXTERNAL(name)>
+and C<XS_INTERNAL(name)> macros to pick the desired linking behaviour.
+The ordinary C<XS(name)> declaration for XSUBs will continue to declare
+non-'static' XSUBs for compatibility, but the XS compiler,
+C<ExtUtils::ParseXS> (C<xsubpp>) will emit 'static' XSUBs by default.
+C<ExtUtils::ParseXS>'s behaviour can be reconfigured from XS using the
+C<EXPORT_XSUB_SYMBOLS> keyword. See L<perlxs> for details.
-XXX
+=head2 Weakening read-only references
-=back
+Weakening read-only references is no longer permitted. It should never
+have worked anyway, and in some cases could result in crashes.
-=head1 Internal Changes
+=head2 Tying scalars that hold typeglobs
-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.
+Attempting to tie a scalar after a typeglob was assigned to it would
+instead tie the handle in the typeglob's IO slot. This meant that it was
+impossible to tie the scalar itself. Similar problems affected C<tied> and
+C<untie>: C<tied $scalar> would return false on a tied scalar if the last
+thing returned was a typeglob, and C<untie $scalar> on such a tied scalar
+would do nothing.
-[ List each change as a =item entry ]
+We fixed this problem before Perl 5.14.0, but it caused problems with some
+CPAN modules, so we put in a deprecation cycle instead.
-=over 4
+Now the deprecation has been removed and this bug has been fixed. So
+C<tie $scalar> will always tie the scalar, not the handle it holds. To tie
+the handle, use C<tie *$scalar> (with an explicit asterisk). The same
+applies to C<tied *$scalar> and C<untie *$scalar>.
-=item *
+=head2 IPC::Open3 no longer provides C<xfork()>, C<xclose_on_exec()>
+and C<xpipe_anon()>
-XXX
+All three functions were private, undocumented and unexported. They do
+not appear to be used by any code on CPAN. Two have been inlined and one
+deleted entirely.
-=back
+=head2 C<$$> no longer caches PID
-=head1 Selected Bug Fixes
+Previously, if one called fork(3) from C, Perl's
+notion of C<$$> could go out of sync with what getpid() returns. By always
+fetching the value of C<$$> via getpid(), this potential bug is eliminated.
+Code that depends on the caching behavior will break. As described in
+L<Core Enhancements|/C<$$> can be assigned to>,
+C<$$> is now writable, but it will be reset during a
+fork.
-XXX Important bug fixes in the core language are summarised here.
-Bug fixes in files in F<ext/> and F<lib/> are best summarised in
-L</Modules and Pragmata>.
+=head2 C<$$> and C<getppid()> no longer emulate POSIX semantics under LinuxThreads
-[ List each fix as a =item entry ]
+The POSIX emulation of C<$$> and C<getppid()> under the obsolete
+LinuxThreads implementation has been removed.
+This only impacts users of Linux 2.4 and
+users of Debian GNU/kFreeBSD up to and including 6.0, not the vast
+majority of Linux installations that use NPTL threads.
-=over 4
+This means that C<getppid()>, like C<$$>, 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 L<$$|perlvar/$$> for details.
+
+=head2 C<< $< >>, C<< $> >>, C<$(> and C<$)> are no longer cached
+
+Similarly to the changes to C<$$> and C<getppid()>, the internal
+caching of C<< $< >>, C<< $> >>, C<$(> and C<$)> 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
+C<sete?[ug]id()> without updating C<PL_e?[ug]id>. Having to deal with
+this complexity wasn't worth it given how cheap the C<gete?[ug]id()>
+system call is.
+
+This change will break a handful of CPAN modules that use the XS-level
+C<PL_uid>, C<PL_gid>, C<PL_euid> or C<PL_egid> variables.
+
+The fix for those breakages is to use C<PerlProc_gete?[ug]id()> to
+retrieve them (e.g. C<PerlProc_getuid()>), and not to assign to
+C<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.
+
+=head2 Which Non-ASCII characters get quoted by C<quotemeta> and C<\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 L<perlfunc/quotemeta>.
+
+=head1 Performance Enhancements
+
+=over
=item *
-C<~~> now correctly handles the precedence of Any~~Object, and is not tricked
-by an overloaded object on the left-hand side.
+Improved performance for Unicode properties in regular expressions
+
+=for comment Can this be compacted some? -- rjbs, 2012-02-20
+
+Matching a code point against a Unicode property is now done via a
+binary search instead of linear. This means for example that the worst
+case for a 1000 item property is 10 probes instead of 1000. This
+inefficiency has been compensated for in the past by permanently storing
+in a hash the results of a given probe plus the results for the adjacent
+64 code points, under the theory that near-by code points are likely to
+be searched for. A separate hash was used for each mention of a Unicode
+property in each regular expression. Thus, C<qr/\p{foo}abc\p{foo}/>
+would generate two hashes. Any probes in one instance would be unknown
+to the other, and the hashes could expand separately to be quite large
+if the regular expression were used on many different widely-separated
+code points. This can lead to running out of memory in extreme cases.
+Now, however, there is just one hash shared by all instances of a given
+property. This means that if C<\p{foo}> is matched against "A" in one
+regular expression in a thread, the result will be known immediately to
+all regular expressions, and the relentless march of using up memory is
+slowed considerably.
=item *
-C<stat _> no longer warns about unopened filehandles [perl #71002].
+Version declarations with the C<use> keyword (e.g., C<use 5.012>) are now
+faster, as they enable features without loading F<feature.pm>.
=item *
-C<stat> on an unopened filehandle now warns consistently, instead of
-skipping the warning at times.
+C<local $_> is faster now, as it no longer iterates through magic that it
+is not going to copy anyway.
=item *
-A change in an earlier 5.15 release caused warning hints to propagate into
-C<do $file>. This has been fixed [rt.cpan.org #72767].
+Perl 5.12.0 sped up the destruction of objects whose classes define
+empty C<DESTROY> methods (to prevent autoloading), by simply not
+calling such empty methods. This release takes this optimisation a
+step further, by not calling any C<DESTROY> method that begins with a
+C<return> statement. This can be useful for destructors that are only
+used for debugging:
+
+ use constant DEBUG => 1;
+ sub DESTROY { return unless DEBUG; ... }
+
+Constant-folding will reduce the first statement to C<return;> if DEBUG
+is set to 0, triggering this optimisation.
=item *
-Starting with 5.12.0, Perl used to get its internal bookkeeping muddled up
-after assigning C<${ qr// }> to a hash element and locking it with
-L<Hash::Util>. This could result in double frees, crashes or erratic
-behaviour.
+Assigning to a variable that holds a typeglob or copy-on-write scalar
+is now much faster. Previously the typeglob would be stringified or
+the copy-on-write scalar would be copied before being clobbered.
=item *
-In 5.15.7, some typeglobs in the CORE namespace were made read-only by
-mistake. This has been fixed [rt.cpan.org #74289].
+Assignment to C<substr> in void context is now more than twice its
+previous speed. Instead of creating and returning a special lvalue
+scalar that is then assigned to, C<substr> modifies the original string
+itself.
=item *
-C<-t> now works when stacked with other filetest operators [perl #77388].
+C<substr> no longer calculates a value to return when called in void
+context.
=item *
-Stacked filetest operators now only call FETCH once on a tied argument.
+Due to changes in L<File::Glob>, Perl's C<glob> function and its C<<
+<...> >> equivalent are now much faster. The splitting of the pattern
+into words has been rewritten in C, resulting in speed-ups of 20% in
+some cases.
+
+This does not affect C<glob> on VMS, as it does not use File::Glob.
=item *
-C</.*/g> would sometimes refuse to match at the end of a string that ends
-with "\n". This has been fixed [perl #109206].
+The short-circuiting operators C<&&>, C<||>, and C<//>, when chained
+(such as C<$a || $b || $c>), are now considerably faster to short-circuit,
+due to reduced optree traversal.
=item *
-Method calls whose arguments were all surrounded with C<my()> or C<our()>
-(as in C<<$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 implementation of C<s///r> makes one fewer copy of the scalar's value.
+
+=item *
-=for comment
-This bug I<did> affect earlier stable releases. It is just the last
-sentence that does not apply to 5.14.
+C<study> is now a no-op.
=item *
-The C<SvPVutf8> C function no longer tries to modify its argument,
-resulting in errors [perl #108994].
+Recursive calls to lvalue subroutines in lvalue scalar context use less
+memory.
+
+=back
+
+=head1 Modules and Pragmata
+
+=head2 Deprecated Modules
+
+=over
+
+=item L<Version::Requirements>
+
+Version::Requirements is now DEPRECATED, use L<CPAN::Meta::Requirements>,
+which is a drop-in replacement. It will be deleted from perl.git blead
+in v5.17.0.
+
+=back
+
+=head2 New Modules and Pragmata
+
+=over 4
=item *
-C<SvPVutf8> now works properly with magical variables.
+L<arybase> -- this new module implements the C<$[> variable.
=item *
-C<SvPVbyte> now works properly non-PVs.
+C<PerlIO::mmap> 0.010 has been added to the Perl core.
+
+The C<mmap> PerlIO layer is no longer implemented by perl itself, but has
+been moved out into the new L<PerlIO::mmap> module.
=back
-=head1 Known Problems
+=head2 Updated Modules and Pragmata
-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, unless
-they were specific to a particular platform (see below).
+This is only an overview of selected module updates. For a complete list of
+updates, run:
-This is a list of some significant unfixed bugs, which are regressions
-from either 5.XXX.XXX or 5.XXX.XXX.
+ $ corelist --diff 5.14.0 5.16.0
-[ List each fix as a =item entry ]
+You can substitute your favorite version in place of 5.14.0, too.
=over 4
=item *
-XXX
+L<XXX> has been upgraded from version 0.69 to version 0.70.
=back
-=head1 Obituary
+=head2 Removed Modules and Pragmata
-XXX If any significant core contributor has died, we've added a short obituary
-here.
+As promised in Perl 5.14.0's release notes, the following modules have
+been removed from the core distribution, and if needed should be installed
+from CPAN instead.
-=head1 Acknowledgements
+=over
+
+=item *
+
+C<Devel::DProf> has been removed from the Perl core. Prior version was
+20110228.00.
+
+=item *
+
+C<Shell> has been removed from the Perl core. Prior version was 0.72_01.
+
+=back
+
+=head1 Documentation
+
+=head2 New Documentation
+
+=head3 L<perldtrace>
+
+L<perldtrace> describes Perl's DTrace support, listing the provided probes
+and gives examples of their use.
+
+=head3 L<perlexperiment>
+
+This document is intended to provide a list of experimental features in
+Perl. It is still a work in progress.
+
+=head3 L<perlootut>
+
+This a new OO tutorial. It focuses on basic OO concepts, and then recommends
+that readers choose an OO framework from CPAN.
+
+=head3 L<perlxstypemap>
+
+The new manual describes the XS typemapping mechanism in unprecedented
+detail and combines new documentation with information extracted from
+L<perlxs> and the previously unofficial list of all core typemaps.
+
+=head2 Changes to Existing Documentation
+
+=head3 L<perlapi>
+
+=over 4
+
+=item *
+
+The HV API has long accepted negative lengths to indicate that the key is
+in UTF8. Now this is documented.
+
+=item *
+
+The C<boolSV()> macro is now documented.
+
+=back
+
+=head3 L<perlfunc>
+
+=over 4
+
+=item *
+
+C<dbmopen> treats a 0 mode as a special case, that prevents a nonexistent
+file from being created. This has been the case since Perl 5.000, but was
+never documented anywhere. Now the perlfunc entry mentions it
+[perl #90064].
+
+=item *
+
+As an accident of history, C<open $fh, "<:", ...> applies the default
+layers for the platform (C<:raw> on Unix, C<:crlf> on Windows), ignoring
+whatever is declared by L<open.pm|open>. This seems such a useful feature
+it has been documented in L<perlfunc|perlfunc/open> and L<open>.
+
+=item *
+
+The entry for C<split> has been rewritten. It is now far clearer than
+before.
+
+=back
+
+=head3 L<perlguts>
+
+=over 4
+
+=item *
+
+A new section, L<Autoloading with XSUBs|perlguts/Autoloading with XSUBs>,
+has been added, which explains the two APIs for accessing the name of the
+autoloaded sub.
+
+=item *
+
+Some of the function descriptions in L<perlguts> were confusing, as it was
+not clear whether they referred to the function above or below the
+description. This has been clarified [perl #91790].
+
+=back
+
+=head3 L<perlobj>
+
+=over 4
+
+=item *
+
+This document has been rewritten from scratch, and its coverage of various OO
+concepts has been expanded.
+
+=back
+
+=head3 L<perlop>
+
+=over 4
+
+=item *
+
+Documentation of the smartmatch operator has been reworked and moved from
+perlsyn to perlop where it belongs.
+
+It has also been corrected for the case of C<undef> on the left-hand
+side. The list of different smart match behaviours had an item in the
+wrong place.
+
+=item *
+
+Documentation of the ellipsis statement (C<...>) has been reworked and
+moved from perlop to perlsyn.
+
+=item *
+
+The explanation of bitwise operators has been expanded to explain how they
+work on Unicode strings (5.14.1).
+
+=item *
+
+More examples for C<m//g> have been added (5.14.1).
+
+=item *
+
+The C<<< <<\FOO >>> here-doc syntax has been documented (5.14.1).
+
+=back
+
+=head3 L<perlpragma>
+
+=over 4
+
+=item *
+
+There is now a standard convention for naming keys in the C<%^H>,
+documented under L<Key naming|perlpragma/Key naming>.
+
+=back
+
+=head3 L<perlsec/Laundering and Detecting Tainted Data>
+
+=over 4
+
+=item *
+
+The example function for checking for taintedness contained a subtle
+error. C<$@> needs to be localized to prevent its changing this
+global's value outside the function. The preferred method to check for
+this remains L<Scalar::Util/tainted>.
+
+=back
+
+=head3 L<perllol>
+
+=over
+
+=item *
+
+L<perllol> has been expanded with examples using the new C<push $scalar>
+syntax introduced in Perl 5.14.0 (5.14.1).
+
+=back
+
+=head3 L<perlmod>
+
+=over
+
+=item *
+
+L<perlmod> now states explicitly that some types of explicit symbol table
+manipulation are not supported. This codifies what was effectively already
+the case [perl #78074].
+
+=back
+
+=head3 L<perlpodstyle>
+
+=over 4
+
+=item *
+
+The tips on which formatting codes to use have been corrected and greatly
+expanded.
+
+=item *
+
+There are now a couple of example one-liners for previewing POD files after
+they have been edited.
+
+=back
+
+=head3 L<perlre>
+
+=over
+
+=item *
+
+The C<(*COMMIT)> directive is now listed in the right section
+(L<Verbs without an argument|perlre/Verbs without an argument>).
+
+=back
+
+=head3 L<perlrun>
+
+=over
+
+=item *
+
+L<perlrun> has undergone a significant clean-up. Most notably, the
+B<-0x...> form of the B<-0> flag has been clarified, and the final section
+on environment variables has been corrected and expanded (5.14.1).
+
+=back
+
+=head3 L<perlsub>
+
+=over
+
+=item *
+
+The ($;) prototype syntax, which has existed for rather a long time, is now
+documented in L<perlsub>. It allows a unary function to have the same
+precedence as a list operator.
+
+=back
+
+=head3 L<perltie>
+
+=over
+
+=item *
+
+The required syntax for tying handles has been documented.
+
+=back
+
+=head3 L<perlvar>
+
+=over
+
+=item *
+
+The documentation for L<$!|perlvar/$!> has been corrected and clarified.
+It used to state that $! could be C<undef>, which is not the case. It was
+also unclear as to whether system calls set C's C<errno> or Perl's C<$!>
+[perl #91614].
+
+=item *
+
+Documentation for L<$$|perlvar/$$> has been amended with additional
+cautions regarding changing the process ID.
+
+=back
+
+=head3 Other Changes
+
+=over 4
+
+=item *
+
+L<perlxs> was extended with documentation on inline typemaps.
+
+=item *
+
+L<perlref> has a new L<Circular References|perlref/Circular References>
+section explaining how circularities may not be freed and how to solve that
+with weak references.
+
+=item *
+
+Parts of L<perlapi> were clarified, and Perl equivalents of some C
+functions have been added as an additional mode of exposition.
+
+=item *
+
+A few parts of L<perlre> and L<perlrecharclass> were clarified.
+
+=back
+
+=head2 Removed Documentation
+
+=head3 Old OO Documentation
+
+All the old OO tutorials, perltoot, perltooc, and perlboot, have been
+removed. The perlbot (bag of object tricks) document has been removed
+as well.
+
+=head3 Development Deltas
+
+The perldelta files for development releases are no longer packaged with
+perl. These can still be found in the perl source code repository.
+
+=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 New Diagnostics
+
+=head3 New Errors
+
+=over 4
+
+=item *
+
+L<Cannot set tied @DB::args|perldiag/"Cannot set tied @DB::args">
+
+This error occurs when C<caller> tries to set C<@DB::args> but finds it
+tied. Before this error was added, it used to crash instead.
+
+=item *
+
+L<Cannot tie unreifiable array|perldiag/"Cannot tie unreifiable array">
+
+This error is part of a safety check that the C<tie> operator does before
+tying a special array like C<@_>. You should never see this message.
+
+=item *
+
+L<&CORE::%s cannot be called directly|perldiag/"&CORE::%s cannot be called directly">
+
+This occurs when a subroutine in the C<CORE::> namespace is called
+with C<&foo> syntax or through a reference. Some subroutines
+in this package cannot yet be called that way, but must be
+called as barewords. See L</Subroutines in the C<CORE> namespace>, above.
+
+=item *
+
+L<Source filters apply only to byte streams|perldiag/"Source filters apply only to byte streams">
+
+This new error occurs when you try to activate a source filter (usually by
+loading a source filter module) within a string passed to C<eval> under the
+C<unicode_eval> feature.
+
+=back
+
+=head3 New Warnings
+
+=over 4
+
+=item *
+
+L<defined(@array) is deprecated|perldiag/"defined(@array) is deprecated">
+
+The long-deprecated C<defined(@array)> now also warns for package variables.
+Previously it only issued a warning for lexical variables.
+
+=item *
+
+L<length() used on %s|perldiag/length() used on %s>
+
+This new warning occurs when C<length> is used on an array or hash, instead
+of C<scalar(@array)> or C<scalar(keys %hash)>.
+
+=item *
+
+L<lvalue attribute %s already-defined subroutine|perldiag/"lvalue attribute %s already-defined subroutine">
+
+L<attributes.pm|attributes> now emits this warning when the :lvalue
+attribute is applied to a Perl subroutine that has already been defined, as
+doing so can have unexpected side-effects.
+
+=item *
+
+L<overload arg '%s' is invalid|perldiag/"overload arg '%s' is invalid">
+
+This warning, in the "overload" category, is produced when the overload
+pragma is given an argument it doesn't recognize, presumably a mistyped
+operator.
+
+=item *
+
+L<$[ used in %s (did you mean $] ?)|perldiag/"$[ used in %s (did you mean $] ?)">
+
+This new warning exists to catch the mistaken use of C<$[> in version
+checks. C<$]>, not C<$[>, contains the version number.
+
+=item *
+
+L<Useless assignment to a temporary|perldiag/"Useless assignment to a temporary">
+
+Assigning to a temporary scalar returned
+from an lvalue subroutine now produces this
+warning [perl #31946].
+
+=item *
+
+L<Useless use of \E|perldiag/"Useless use of \E">
+
+C<\E> does nothing unless preceded by C<\Q>, C<\L> or C<\U>.
+
+=back
+
+=head2 Removed Errors
+
+=over
+
+=item *
+
+"sort is now a reserved word"
+
+This error used to occur when C<sort> was called without arguments,
+followed by C<;> or C<)>. (E.g., C<sort;> would die, but C<{sort}> was
+OK.) This error message was added in Perl 3 to catch code like
+C<close(sort)> which would no longer work. More than two decades later,
+this message is no longer appropriate. Now C<sort> without arguments is
+always allowed, and returns an empty list, as it did in those cases
+where it was already allowed [perl #90030].
+
+=back
+
+=head2 Changes to Existing Diagnostics
+
+=over 4
+
+=item *
+
+The "Applying pattern match..." or similar warning produced when an
+array or hash is on the left-hand side of the C<=~> operator now
+mentions the name of the variable.
+
+=item *
+
+The "Attempt to free non-existent shared string" has had the spelling
+of "non-existent" corrected to "nonexistent". It was already listed
+with the correct spelling in L<perldiag>.
+
+=item *
+
+The error messages for using C<default> and C<when> outside of a
+topicalizer have been standardised to match the messages for C<continue>
+and loop controls. They now read 'Can't "default" outside a
+topicalizer' and 'Can't "when" outside a topicalizer'. They both used
+to be 'Can't use when() outside a topicalizer' [perl #91514].
+
+=item *
+
+The message, "Code point 0x%X is not Unicode, no properties match it;
+all inverse properties do" has been changed to "Code point 0x%X is not
+Unicode, all \p{} matches fail; all \P{} matches succeed".
+
+=item *
+
+Redefinition warnings for constant subroutines used to be mandatory,
+even occurring under C<no warnings>. Now they respect the L<warnings>
+pragma.
+
+=item *
+
+The "glob failed" warning message is now suppressible via C<no warnings>
+[perl #111656].
+
+=item *
+
+The L<Invalid version format|perldiag/"Invalid version format (%s)">
+error message now says "negative version number" within the parentheses,
+rather than "non-numeric data", for negative numbers.
+
+=item *
+
+The two warnings
+L<Possible attempt to put comments in qw() list|perldiag/"Possible attempt to put comments in qw() list">
+and
+L<Possible attempt to separate words with commas|perldiag/"Possible attempt to separate words with commas">
+are no longer mutually exclusive: the same C<qw> construct may produce
+both.
+
+=item *
+
+The uninitialized warning for C<y///r> when C<$_> is implicit and
+undefined now mentions the variable name, just like the non-/r variation
+of the operator.
+
+=item *
+
+The 'Use of "foo" without parentheses is ambiguous' warning has been
+extended to apply also to user-defined subroutines with a (;$)
+prototype, and not just to built-in functions.
+
+=item *
+
+Warnings that mention the names of lexical (C<my>) variables with
+Unicode characters in them now respect the presence or absence of the
+C<:utf8> layer on the output handle, instead of outputting UTF8
+regardless. Also, the correct names are included in the strings passed
+to C<$SIG{__WARN__}> handlers, rather than the raw UTF8 bytes.
+
+=back
+
+=head1 Utility Changes
+
+=head3 L<h2ph>
+
+=over 4
+
+=item *
+
+L<h2ph> used to generate code of the form
+
+ unless(defined(&FOO)) {
+ sub FOO () {42;}
+ }
+
+But the subroutine is a compile-time declaration, and is hence unaffected
+by the condition. It has now been corrected to emit a string C<eval>
+around the subroutine [perl #99368].
+
+=back
+
+=head3 L<splain>
+
+=over 4
+
+=item *
+
+F<splain> no longer emits backtraces with the first line number repeated.
+
+This:
+
+ Uncaught exception from user code:
+ Cannot fwiddle the fwuddle at -e line 1.
+ at -e line 1
+ main::baz() called at -e line 1
+ main::bar() called at -e line 1
+ main::foo() called at -e line 1
+
+has become this:
+
+ Uncaught exception from user code:
+ Cannot fwiddle the fwuddle at -e line 1.
+ main::baz() called at -e line 1
+ main::bar() called at -e line 1
+ main::foo() called at -e line 1
+
+=item *
+
+Some error messages consist of multiple lines that are listed as separate
+entries in L<perldiag>. splain has been taught to find the separate
+entries in these cases, instead of simply failing to find the message.
+
+=back
+
+=head3 L<zipdetails>
+
+=over 4
+
+=item *
+
+This is a new utility, included as part of an
+L<IO::Compress::Base> upgrade.
+
+L<zipdetails> displays information about the internal record structure
+of the zip file. It is not concerned with displaying any details of
+the compressed data stored in the zip file.
+
+=back
+
+=head1 Configuration and Compilation
+
+=over 4
+
+=item *
+
+F<regexp.h> has been modified for compatibility with GCC's B<-Werror>
+option, as used by some projects that include perl's header files (5.14.1).
+
+=item *
+
+C<USE_LOCALE{,_COLLATE,_CTYPE,_NUMERIC}> have been added the output of perl -V
+as they have affect the behaviour of the interpreter binary (albeit only
+in a small area).
+
+=item *
+
+The code and tests for L<IPC::Open2> have been moved from F<ext/IPC-Open2>
+into F<ext/IPC-Open3>, as C<IPC::Open2::open2()> is implemented as a thin
+wrapper around C<IPC::Open3::_open3()>, and hence is very tightly coupled to
+it.
+
+=item *
+
+The magic types and magic vtables are now generated from data in a new script
+F<regen/mg_vtable.pl>, instead of being maintained by hand. As different
+EBCDIC variants can't agree on the code point for '~', the character to code
+point conversion is done at build time by F<generate_uudmap> to a new generated
+header F<mg_data.h>. C<PL_vtbl_bm> and C<PL_vtbl_fm> are now defined by the
+pre-processor as C<PL_vtbl_regexp>, instead of being distinct C variables.
+C<PL_vtbl_sig> has been removed.
+
+=item *
+
+Building with C<-DPERL_GLOBAL_STRUCT> works again. This configuration is not
+generally used.
+
+=item *
+
+Perl configured with I<MAD> now correctly frees C<MADPROP> structures when
+OPs are freed. C<MADPROP>s are now allocated with C<PerlMemShared_malloc()>
+
+=item *
+
+F<makedef.pl> has been refactored. This should have no noticeable affect on
+any of the platforms that use it as part of their build (AIX, VMS, Win32).
+
+=item *
+
+C<useperlio> can no longer be disabled.
+
+=item *
+
+The file F<global.sym> is no longer needed, and has been removed. It
+contained a list of all exported functions, one of the files generated by
+F<regen/embed.pl> from data in F<embed.fnc> and F<regen/opcodes>. The code
+has been refactored so that the only user of F<global.sym>, F<makedef.pl>,
+now reads F<embed.fnc> and F<regen/opcodes> directly, removing the need to
+store the list of exported functions in an intermediate file.
+
+As F<global.sym> was never installed, this change should not be visible
+outside the build process.
+
+=item *
+
+F<pod/buildtoc>, used by the build process to build L<perltoc>, has been
+refactored and simplified. It now only contains code to build L<perltoc>;
+the code to regenerate Makefiles has been moved to F<Porting/pod_rules.pl>.
+It's a bug if this change has any material effect on the build process.
+
+=item *
+
+F<pod/roffitall> is now built by F<pod/buildtoc>, instead of being
+shipped with the distribution. Its list of manpages is now generated
+(and therefore current). See also RT #103202 for an unresolved related
+issue.
+
+=item *
+
+The man page for C<XS::Typemap> is no longer installed. C<XS::Typemap>
+is a test module which is not installed, hence installing its
+documentation makes no sense.
+
+=item *
+
+The -Dusesitecustomize and -Duserelocatableinc options now work
+together properly.
+
+=back
+
+=head1 Platform Support
+
+=head2 Platform-Specific Notes
+
+=head3 Cygwin
+
+=over 4
+
+=item *
+
+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
+F<README.cygwin> for a discussion of the newly-added
+C<Cygwin::sync_winenv()> function [perl #110190] and for
+further links.
+
+=back
+
+=head3 HP-UX
+
+=over 4
+
+=item *
+
+HP-UX PA-RISC/64 now supports gcc-4.x
+
+A fix to correct the socketsize now makes the test suite pass on HP-UX
+PA-RISC for 64bitall builds.
+
+=back
+
+=head3 VMS
+
+=over 4
+
+=item *
+
+Remove unnecessary includes, fix miscellaneous compiler warnings and
+close some unclosed comments on F<vms/vms.c>.
+
+Remove sockadapt layer from the VMS build.
+
+=item *
+
+Explicit support for VMS versions prior to v7.0 and DEC C versions
+prior to v6.0 has been removed.
+
+=item *
+
+Since Perl 5.10.1, the home-grown C<stat> wrapper has been unable to
+distinguish between a directory name containing an underscore and an
+otherwise-identical filename containing a dot in the same position
+(e.g., t/test_pl as a directory and t/test.pl as a file). This problem
+has been corrected.
+
+=item *
+
+The build on VMS now allows names of the resulting symbols in C code for
+Perl longer than 31 characters. Symbols like
+C<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.
+
+=back
+
+=head3 GNU/Hurd
+
+Numerous build and test failures on GNU/Hurd have been resolved with hints
+for building DBM modules, detection of the library search path, and enabling
+of large file support.
+
+=head3 OpenVOS
+
+Perl is now built with dynamic linking on OpenVOS, the minimum supported
+version of which is now Release 17.1.0.
+
+=head3 SunOS
+
+The CC workshop C++ compiler is now detected and used on systems that ship
+without cc.
+
+=head1 Internal Changes
+
+=over 4
+
+=item *
+
+The compiled representation of formats is now stored via the C<mg_ptr> of
+their C<PERL_MAGIC_fm>. Previously it was stored in the string buffer,
+beyond C<SvLEN()>, the regular end of the string. C<SvCOMPILED()> and
+C<SvCOMPILED_{on,off}()> now exist solely for compatibility for XS code.
+The first is always 0, the other two now no-ops. (5.14.1)
+
+=item *
+
+Some global variables have been marked C<const>, members in the interpreter
+structure have been re-ordered, and the opcodes have been re-ordered. The
+op C<OP_AELEMFAST> has been split into C<OP_AELEMFAST> and C<OP_AELEMFAST_LEX>.
+
+=item *
+
+When empting a hash of its elements (e.g. via undef(%h), or %h=()), HvARRAY
+field is no longer temporarily zeroed. Any destructors called on the freed
+elements see the remaining elements. Thus, %h=() becomes more like
+C<delete $h{$_} for keys %h>.
+
+=item *
+
+Boyer-Moore compiled scalars are now PVMGs, and the Boyer-Moore tables are now
+stored via the mg_ptr of their C<PERL_MAGIC_bm>.
+Previously they were PVGVs, with the tables stored in
+the string buffer, beyond C<SvLEN()>. This eliminates
+the last place where the core stores data beyond C<SvLEN()>.
+
+=item *
+
+Simplified logic in C<Perl_sv_magic()> introduces a small change of
+behaviour for error cases involving unknown magic types. Previously, if
+C<Perl_sv_magic()> was passed a magic type unknown to it, it would
+
+=over
+
+=item 1.
+
+Croak "Modification of a read-only value attempted" if read only
+
+=item 2.
+
+Return without error if the SV happened to already have this magic
+
+=item 3.
+
+otherwise croak "Don't know how to handle magic of type \\%o"
+
+=back
+
+Now it will always croak "Don't know how to handle magic of type \\%o", even
+on read only values, or SVs which already have the unknown magic type.
+
+=item *
+
+The experimental C<fetch_cop_label> function has been renamed to
+C<cop_fetch_label>.
+
+=item *
+
+The C<cop_store_label> function has been added to the API, but is
+experimental.
+
+=item *
+
+F<embedvar.h> has been simplified, and one level of macro indirection for
+PL_* variables has been removed for the default (non-multiplicity)
+configuration. PERLVAR*() macros now directly expand their arguments to
+tokens such as C<PL_defgv>, instead of expanding to C<PL_Idefgv>, with
+F<embedvar.h> defining a macro to map C<PL_Idefgv> to C<PL_defgv>. XS code
+which has unwarranted chumminess with the implementation may need updating.
+
+=item *
+
+A C<coreargs> opcode has been added, to be used by C<&CORE::foo> subs to sort
+out C<@_>.
+
+=item *
+
+An API has been added to explicitly choose whether or not to export XSUB
+symbols. More detail can be found in the comments for commit e64345f8.
+
+=item *
+
+The C<is_gv_magical_sv> function has been eliminated and merged with
+C<gv_fetchpvn_flags>. It used to be called to determine whether a GV
+should be autovivified in rvalue context. Now it has been replaced with a
+new C<GV_ADDMG> flag (not part of the API).
+
+=item *
+
+The returned code point from the function C<utf8n_to_uvuni()>
+when the input is malformed UTF-8, malformations are allowed, and
+C<utf8> warnings are off is now the Unicode REPLACEMENT CHARACTER
+whenever the malformation is such that no well-defined code point can be
+computed. Previously the returned value was essentially garbage. The
+only malformations that have well-defined values are a zero-length
+string (0 is the return), and overlong UTF-8 sequences.
+
+=item *
+
+The returned code point from the function C<utf8n_to_uvuni()>
+when the input is malformed UTF-8, malformations are allowed, and
+C<utf8> warnings are off is now the Unicode REPLACEMENT CHARACTER
+whenever the malformation is such that no well-defined code point can be
+computed. Previously the returned value was essentially garbage. The
+only malformations that have well-defined values are a zero-length
+string (0 is the return), and overlong UTF-8 sequences.
+
+=item *
+
+Padlists are now marked C<AvREAL>; i.e., reference-counted. They have
+always been reference-counted, but were not marked real, because F<pad.c>
+did its own clean-up, instead of using the usual clean-up code in F<sv.c>.
+That caused problems in thread cloning, so now the C<AvREAL> flag is on,
+but is turned off in F<pad.c> right before the padlist is freed (after
+F<pad.c> has done its custom freeing of the pads).
+
+=item *
+
+All the C files that make up the Perl core have been converted to UTF-8.
+
+=item *
+
+These new functions have been added as part of the work on Unicode symbols:
+
+ HvNAMELEN
+ HvNAMEUTF8
+ HvENAMELEN
+ HvENAMEUTF8
+ gv_init_pv
+ gv_init_pvn
+ gv_init_pvsv
+ gv_fetchmeth_pv
+ gv_fetchmeth_pvn
+ gv_fetchmeth_sv
+ gv_fetchmeth_pv_autoload
+ gv_fetchmeth_pvn_autoload
+ gv_fetchmeth_sv_autoload
+ gv_fetchmethod_pv_flags
+ gv_fetchmethod_pvn_flags
+ gv_fetchmethod_sv_flags
+ gv_autoload_pv
+ gv_autoload_pvn
+ gv_autoload_sv
+ newGVgen_flags
+ sv_derived_from_pv
+ sv_derived_from_pvn
+ sv_derived_from_sv
+ sv_does_pv
+ sv_does_pvn
+ sv_does_sv
+ whichsig_pv
+ whichsig_pvn
+ whichsig_sv
+ newCONSTSUB_flags
+
+The gv_fetchmethod_*_flags functions, like gv_fetchmethod_flags, are
+experimental and may change in a future release.
+
+=item *
+
+The following functions were added. These are I<not> part of the API:
+
+ GvNAMEUTF8
+ GvENAMELEN
+ GvENAME_HEK
+ CopSTASH_flags
+ CopSTASH_flags_set
+ PmopSTASH_flags
+ PmopSTASH_flags_set
+ sv_sethek
+ HEKfARG
+
+There is also a C<HEKf> macro corresponding to C<SVf>, for
+interpolating HEKs in formatted strings.
+
+=item *
+
+C<sv_catpvn_flags> takes a couple of new internal-only flags,
+C<SV_CATBYTES> and C<SV_CATUTF8>, which tell it whether the char array to
+be concatenated is UTF8. This allows for more efficient concatenation than
+creating temporary SVs to pass to C<sv_catsv>.
+
+=item *
+
+For XS AUTOLOAD subs, $AUTOLOAD is set once more, as it was in 5.6.0. This
+is in addition to setting C<SvPVX(cv)>, for compatibility with 5.8 to 5.14.
+See L<perlguts/Autoloading with XSUBs>.
+
+=item *
+
+Perl now checks whether the array (the linearised isa) returned by a MRO
+plugin begins with the name of the class itself, for which the array was
+created, instead of assuming that it does. This prevents the first element
+from being skipped during method lookup. It also means that
+C<mro::get_linear_isa> may return an array with one more element than the
+MRO plugin provided [perl #94306].
+
+=item *
+
+C<PL_curstash> is now reference-counted.
+
+=item *
+
+There are now feature bundle hints in C<PL_hints> (C<$^H>) that version
+declarations use, to avoid having to load F<feature.pm>. One setting of
+the hint bits indicates a "custom" feature bundle, which means that the
+entries in C<%^H> still apply. F<feature.pm> uses that.
+
+The C<HINT_FEATURE_MASK> macro is defined in F<perl.h> along with other
+hints. Other macros for setting and testing features and bundles are in
+the new F<feature.h>. C<FEATURE_IS_ENABLED> (which has moved to
+F<feature.h>) is no longer used throughout the codebase, but more specific
+macros, e.g., C<FEATURE_SAY_IS_ENABLED>, that are defined in F<feature.h>.
+
+=item *
+
+F<lib/feature.pm> is now a generated file, created by the new
+F<regen/feature.pl> script, which also generates F<feature.h>.
+
+=item *
+
+Tied arrays are now always C<AvREAL>. If C<@_> or C<DB::args> is tied, it
+is reified first, to make sure this is always the case.
+
+=item *
+
+Two new functions C<utf8_to_uvchr_buf()> and C<utf8_to_uvuni_buf()> have
+been added. These are the same as C<utf8_to_uvchr> and
+C<utf8_to_uvuni> (which are now deprecated), but take an extra parameter
+that is used to guard against reading beyond the end of the input
+string.
+See L<perlapi/utf8_to_uvchr_buf> and L<perlapi/utf8_to_uvuni_buf>.
+
+=item *
+
+The regular expression engine now does TRIE case insensitive matches
+under Unicode. This may change the output of C<< use re 'debug'; >>,
+and will speed up various things.
+
+=item *
+
+There is a new C<wrap_op_checker()> function, which provides a thread-safe
+alternative to writing to C<PL_check> directly.
+
+=back
+
+=head1 Selected Bug Fixes
+
+=head2 Array and hash
+
+=over
+
+=item *
+
+A bug has been fixed that would cause a "Use of freed value in iteration"
+error if the next two hash elements that would be iterated over are
+deleted [perl #85026]. (5.14.1)
+
+=item *
+
+Deleting the current hash iterator (the hash element that would be returend
+by the next call to C<each>) in void context used not to free it
+[perl #85026].
+
+=item *
+
+Deletion of methods via C<delete $Class::{method}> syntax used to update
+method caches if called in void context, but not scalar or list context.
+
+=item *
+
+When hash elements are deleted in void context, the internal hash entry is
+now freed before the value is freed, to prevent destructors called by that
+latter freeing from seeing the hash in an inconsistent state. It was
+possible to cause double-frees if the destructor freed the hash itself
+[perl #100340].
+
+=item *
+
+A C<keys> optimisation in Perl 5.12.0 to make it faster on empty hashes
+caused C<each> not to reset the iterator if called after the last element
+was deleted.
+
+=item *
+
+Freeing deeply nested hashes no longer crashes [perl #44225].
+
+=item *
+
+It is possible from XS code to create hashes with elements that have no
+values. The hash element and slice operators used to crash
+when handling these in lvalue context. They now
+produce a "Modification of non-creatable hash value attempted" error
+message.
+
+=item *
+
+If list assignment to a hash or array triggered destructors that freed the
+hash or array itself, a crash would ensue. This is no longer the case
+[perl #107440].
+
+=item *
+
+It used to be possible to free the typeglob of a localised array or hash
+(e.g., C<local @{"x"}; delete $::{x}>), resulting in a crash on scope exit.
+
+=item *
+
+Some core bugs affecting L<Hash::Util> have been fixed: locking a hash
+element that is a glob copy no longer causes subsequent assignment to it to
+corrupt the glob, and unlocking a hash element that holds a copy-on-write
+scalar no longer causes modifications to that scalar to modify other
+scalars that were sharing the same string buffer.
+
+=back
+
+=head2 C API fixes
+
+=over
+
+=item *
+
+The C<newHVhv> XS function now works on tied hashes, instead of crashing or
+returning an empty hash.
+
+=item *
+
+The C<SvIsCOW> C macro now returns false for read-only copies of typeglobs,
+such as those created by:
+
+ $hash{elem} = *foo;
+ Hash::Util::lock_value %hash, 'elem';
+
+It used to return true.
+
+=item *
+
+The C<SvPVutf8> C function no longer tries to modify its argument,
+resulting in errors [perl #108994].
+
+=item *
+
+C<SvPVutf8> now works properly with magical variables.
+
+=item *
+
+C<SvPVbyte> now works properly non-PVs.
+
+=item *
+
+When presented with malformed UTF-8 input, the XS-callable functions
+C<is_utf8_string()>, C<is_utf8_string_loc()>, and
+C<is_utf8_string_loclen()> could read beyond the end of the input
+string by up to 12 bytes. This no longer happens. [perl #32080].
+However, currently, C<is_utf8_char()> still has this defect, see
+L</is_utf8_char()> above.
+
+=item *
+
+The C-level C<pregcomp> function could become confused as to whether the
+pattern was in UTF8 if the pattern was an overloaded, tied, or otherwise
+magical scalar [perl #101940].
+
+=back
+
+=head2 Compile-time hints
+
+=over
+
+=item *
+
+Tying C<%^H> no longer causes perl to crash or ignore the contents of
+C<%^H> when entering a compilation scope [perl #106282].
+
+=item *
+
+C<eval $string> and C<require> used not to
+localise C<%^H> during compilation if it
+was empty at the time the C<eval> call itself was compiled. This could
+lead to scary side effects, like C<use re "/m"> enabling other flags that
+the surrounding code was trying to enable for its caller [perl #68750].
+
+=item *
+
+C<eval $string> and C<require> no longer localise hints (C<$^H> and C<%^H>)
+at run time, but only during compilation of the $string or required file.
+This makes C<BEGIN { $^H{foo}=7 }> equivalent to
+C<BEGIN { eval '$^H{foo}=7' }> [perl #70151].
+
+=item *
+
+Creating a BEGIN block from XS code (via C<newXS> or C<newATTRSUB>) would,
+on completion, make the hints of the current compiling code the current
+hints. This could cause warnings to occur in a non-warning scope.
+
+=back
+
+=head2 Copy-on-write scalars
+
+Copy-on-write or shared hash key scalars
+were introduced in 5.8.0, but most Perl code
+did not encounter them (they were used mostly internally). Perl
+5.10.0 extended them, such that assigning C<__PACKAGE__> or a
+hash key to a scalar would make it copy-on-write. Several parts
+of Perl were not updated to account for them, but have now been fixed.
+
+=over
+
+=item *
+
+C<utf8::decode> had a nasty bug that would modify copy-on-write scalars'
+string buffers in place (i.e., skipping the copy). This could result in
+hashes having two elements with the same key [perl #91834].
+
+=item *
+
+Lvalue subroutines were not allowing COW scalars to be returned. This was
+fixed for lvalue scalar context in Perl 5.12.3 and 5.14.0, but list context
+was not fixed until this release.
+
+=item *
+
+Elements of restricted hashes (see the L<fields> pragma) containing
+copy-on-write values couldn't be deleted, nor could such hashes be cleared
+(C<%hash = ()>).
+
+=item *
+
+Localising a tied variable used to make it read-only if it contained a
+copy-on-write string.
+
+=item *
+
+Assigning a copy-on-write string to a stash
+element no longer causes a double free. Regardless of this change, the
+results of such assignments are still undefined.
+
+=item *
+
+Assigning a copy-on-write string to a tied variable no longer stops that
+variable from being tied if it happens to be a PVMG or PVLV internally.
+
+=item *
+
+Doing a substitution on a tied variable returning a copy-on-write
+scalar used to cause an assertion failure or an "Attempt to free
+nonexistent shared string" warning.
+
+=item *
+
+This one is a regression from 5.12: In 5.14.0, the bitwise assignment
+operators C<|=>, C<^=> and C<&=> started leaving the left-hand side
+undefined if it happened to be a copy-on-write string [perl #108480].
+
+=item *
+
+L<Storable>, L<Devel::Peek> and L<PerlIO::scalar> had similar problems.
+See L</Updated Modules and Pragmata>, above.
+
+=back
+
+=head2 The debugger
+
+=over
+
+=item *
+
+F<dumpvar.pl>, and consequently the C<x> command in the debugger, have been
+fixed to handle objects blessed into classes whose names contain "=". The
+contents of such objects used not to be dumped [perl #101814].
+
+=item *
+
+The "R" command for restarting a debugger session has been fixed to work on
+Windows, or any other system lacking a C<POSIX::_SC_OPEN_MAX> constant
+[perl #87740].
+
+=item *
+
+The C<#line 42 foo> directive used not to update the arrays of lines used
+by the debugger if it occurred in a string eval. This was partially fixed
+in 5.14, but it only worked for a single C<#line 42 foo> in each eval. Now
+it works for multiple.
+
+=item *
+
+When subroutine calls are intercepted by the debugger, the name of the
+subroutine or a reference to it is stored in C<$DB::sub>, for the debugger
+to access. In some cases (such as C<$foo = *bar; undef *bar; &$foo>)
+C<$DB::sub> would be set to a name that could not be used to find the
+subroutine, and so the debugger's attempt to call it would fail. Now the
+check to see whether a reference is needed is more robust, so those
+problems should not happen anymore [rt.cpan.org #69862].
+
+=item *
+
+Every subroutine has a filename associated with it that the debugger uses.
+The one associated with constant subroutines used to be misallocated when
+cloned under threads. Consequently, debugging threaded applications could
+result in memory corruption [perl #96126].
+
+=back
+
+=head2 Dereferencing operators
+
+=over
+
+=item *
+
+C<defined(${"..."})>, C<defined(*{"..."})>, etc., used to
+return true for most, but not all built-in variables, if
+they had not been used yet. This bug affected C<${^GLOBAL_PHASE}> and
+C<${^UTF8CACHE}>, among others. It also used to return false if the
+package name was given as well (C<${"::!"}>) [perl #97978, #97492].
+
+=item *
+
+Perl 5.10.0 introduced a similar bug: C<defined(*{"foo"})> where "foo"
+represents the name of a built-in global variable used to return false if
+the variable had never been used before, but only on the I<first> call.
+This, too, has been fixed.
+
+=item *
+
+Since 5.6.0, C<*{ ... }> has been inconsistent in how it treats undefined
+values. It would die in strict mode or lvalue context for most undefined
+values, but would be treated as the empty string (with a warning) for the
+specific scalar return by C<undef()> (C<&PL_sv_undef> internally). This
+has been corrected. C<undef()> is now treated like other undefined
+scalars, as in Perl 5.005.
+
+=back
+
+=head2 Filehandle, last-accessed
+
+Perl has an internal variable that stores the last filehandle to be
+accessed. It is used by C<$.> and by C<tell> and C<eof> without
+arguments.
+
+=over
+
+=item *
+
+It used to be possible to set this internal variable to a glob copy and
+then modify that glob copy to be something other than a glob, and still
+have the last-accessed filehandle associated with the variable after
+assigning a glob to it again:
+
+ my $foo = *STDOUT; # $foo is a glob copy
+ <$foo>; # $foo is now the last-accessed handle
+ $foo = 3; # no longer a glob
+ $foo = *STDERR; # still the last-accessed handle
+
+Now the C<$foo = 3> assignment unsets that internal variable, so there
+is no last-accessed filehandle, just as if C<< <$foo> >> had never
+happened.
+
+This also prevents some unrelated handle from becoming the last-accessed
+handle if $foo falls out of scope and the same internal SV gets used for
+another handle [perl #97988].
+
+=item *
+
+A regression in 5.14 caused these statements not to set that internal
+variable:
+
+ my $fh = *STDOUT;
+ tell $fh;
+ eof $fh;
+ seek $fh, 0,0;
+ tell *$fh;
+ eof *$fh;
+ seek *$fh, 0,0;
+ readline *$fh;
+
+This is now fixed, but C<tell *{ *$fh }> still has the problem, and it
+is not clear how to fix it [perl #106536].
+
+=back
+
+=head2 Filetests and C<stat>
+
+The term "filetests" refers to the operators that consist of a hyphen
+followed by a single letter: C<-r>, C<-x>, C<-M>, etc. The term "stacked"
+when applied to filetests means followed by another filetest operator
+sharing the same operand, as in C<-r -x -w $fooo>.
+
+=over
+
+=item *
+
+C<stat> produces more consistent warnings. It no longer warns for "_"
+[perl #71002] and no longer skips the warning at times for other unopened
+handles. It no longer warns about an unopened handle when the operating
+system's C<fstat> function fails.
+
+=item *
+
+C<stat> would sometimes return negative numbers for large inode numbers,
+because it was using the wrong internal C type. [perl #84590]
+
+=item *
+
+C<lstat> is documented to fall back to C<stat> (with a warning) when given
+a filehandle. When passed an IO reference, it was actually doing the
+equivalent of S<C<stat _>> and ignoring the handle.
+
+=item *
+
+C<-T _> with no preceding C<stat> used to produce a
+confusing "uninitialized" warning, even though there
+is no visible uninitialized value to speak of.
+
+=item *
+
+C<-T>, C<-B>, C<-l> and C<-t> now work
+when stacked with other filetest operators
+[perl #77388].
+
+=item *
+
+In 5.14.0, filetest ops (C<-r>, C<-x>, etc.) started calling FETCH on a
+tied argument belonging to the previous argument to a list operator, if
+called with a bareword argument or no argument at all. This has been
+fixed, so C<push @foo, $tied, -r> no longer calls FETCH on C<$tied>.
+
+=item *
+
+In Perl 5.6, C<-l> followed by anything other than a bareword would treat
+its argument as a file name. That was changed in 5.8 for glob references
+(C<\*foo>), but not for globs themselves (C<*foo>). C<-l> started
+returning C<undef> for glob references without setting the last
+stat buffer that the "_" handle uses, but only if warnings
+were turned on. With warnings off, it was the same as 5.6.
+In other words, it was simply buggy and inconsistent. Now the 5.6
+behaviour has been restored.
+
+=item *
+
+C<-l> followed by a bareword no longer "eats" the previous argument to
+the list operator in whose argument list it resides. Hence,
+C<print "bar", -l foo> now actually prints "bar", because C<-l>
+on longer eats it.
+
+=item *
+
+Perl keeps several internal variables to keep track of the last stat
+buffer, from which file(handle) it originated, what type it was, and
+whether the last stat succeeded.
+
+There were various cases where these could get out of synch, resulting in
+inconsistent or erratic behaviour in edge cases (every mention of C<-T>
+applies to C<-B> as well):
+
+=over
+
+=item *
+
+C<-T I<HANDLE>>, even though it does a C<stat>, was not resetting the last
+stat type, so an C<lstat _> following it would merrily return the wrong
+results. Also, it was not setting the success status.
+
+=item *
+
+Freeing the handle last used by C<stat> or a filetest could result in
+S<C<-T _>> using an unrelated handle.
+
+=item *
+
+C<stat> with an IO reference would not reset the stat type or record the
+filehandle for S<C<-T _>> to use.
+
+=item *
+
+Fatal warnings could cause the stat buffer not to be reset
+for a filetest operator on an unopened filehandle or C<-l> on any handle.
+Fatal warnings also stopped C<-T> from setting C<$!>.
+
+=item *
+
+When the last stat was on an unreadable file, C<-T _> is supposed to
+return C<undef>, leaving the last stat buffer unchanged. But it was
+setting the stat type, causing C<lstat _> to stop working.
+
+=item *
+
+C<-T I<FILENAME>> was not resetting the internal stat buffers for
+unreadable files.
+
+=back
+
+These have all been fixed.
+
+=back
+
+=head2 Formats
+
+=over
+
+=item *
+
+A number of edge cases have been fixed with formats and C<formline>;
+in particular, where the format itself is potentially variable (such as
+with ties and overloading), and where the format and data differ in their
+encoding. In both these cases, it used to possible for the output to be
+corrupted [perl #91032].
+
+=item *
+
+C<formline> no longer converts its argument into a string in-place. So
+passing a reference to C<formline> no longer destroys the reference
+[perl #79532].
+
+=item *
+
+Assignment to C<$^A> (the format output accumulator) now recalculates
+the number of lines output.
+
+=back
+
+=head2 C<given> and C<when>
+
+=over
+
+=item *
+
+C<given> was not scoping its implicit $_ properly, resulting in memory
+leaks or "Variable is not available" warnings [perl #94682].
+
+=item *
+
+C<given> was not calling set-magic on the implicit lexical C<$_> that it
+uses. This meant, for example, that C<pos> would be remembered from one
+execution of the same C<given> block to the next, even if the input were a
+different variable [perl #84526].
+
+=item *
+
+C<when> blocks are now capable of returning variables declared inside the
+enclosing C<given> block [perl #93548].
+
+=back
+
+=head2 The C<glob> operator
+
+=over
+
+=item *
+
+On OSes other than VMS, Perl's C<glob> operator (and the C<< <...> >> form)
+use L<File::Glob> underneath. L<File::Glob> splits the pattern into words,
+before feeding each word to its C<bsd_glob> function.
+
+There were several inconsistencies in the way the split was done. Now
+quotation marks (' and ") are always treated as shell-style word delimiters
+(that allow whitespace as part of a word) and backslashes are always
+preserved, unless they exist to escape quotation marks. Before, those
+would only sometimes be the case, depending on whether the pattern
+contained whitespace. Also, escaped whitespace at the end of the pattern
+is no longer stripped [perl #40470].
+
+=item *
+
+C<CORE::glob> now works as a way to call the default globbing function. It
+used to respect overrides, despite the C<CORE::> prefix.
+
+=item *
+
+Under miniperl (used to configure modules when perl itself is built),
+C<glob> now clears %ENV before calling csh, since the latter croaks on some
+systems if it does not like the contents of the LS_COLORS enviroment
+variable [perl #98662].
+
+=back
+
+=head2 Lvalue subroutines
+
+=over
+
+=item *
+
+Explicit return now returns the actual argument passed to return, instead
+of copying it [perl #72724, #72706].
+
+=item *
+
+Lvalue subroutines used to enforce lvalue syntax (i.e., whatever can go on
+the left-hand side of C<=>) for the last statement and the arguments to
+return. Since lvalue subroutines are not always called in lvalue context,
+this restriction has been lifted.
+
+=item *
+
+Lvalue subroutines are less restrictive as to what values can be returned.
+It used to croak on values returned by C<shift> and C<delete> and from
+other subroutines, but no longer does so [perl #71172].
+
+=item *
+
+Empty lvalue subroutines (C<sub :lvalue {}>) used to return C<@_> in list
+context. In fact, all subroutines used to, but regular subs were fixed in
+Perl 5.8.2. Now lvalue subroutines have been likewise fixed.
+
+=item *
+
+Autovivification now works on values returned from lvalue subroutines
+[perl #7946], as does returning C<keys> in lvalue context.
+
+=item *
+
+Lvalue subroutines used to copy their return values in rvalue context. Not
+only was this a waste of CPU cycles, but it also caused bugs. A C<($)>
+prototype would cause an lvalue sub to copy its return value [perl #51408],
+and C<while(lvalue_sub() =~ m/.../g) { ... }> would loop endlessly
+[perl #78680].
+
+=item *
+
+When called in potential lvalue context
+(e.g., subroutine arguments or a list
+passed to C<for>), lvalue subroutines used to copy
+any read-only value that was returned. E.g., C< sub :lvalue { $] } >
+would not return C<$]>, but a copy of it.
+
+=item *
+
+When called in potential lvalue context, an lvalue subroutine returning
+arrays or hashes used to bind the arrays or hashes to scalar variables,
+resulting in bugs. This was fixed in 5.14.0 if an array were the first
+thing returned from the subroutine (but not for C<$scalar, @array> or
+hashes being returned). Now a more general fix has been applied
+[perl #23790].
+
+=item *
+
+Method calls whose arguments were all surrounded with C<my()> or C<our()>
+(as in C<< $object->method(my($a,$b)) >>) used to force lvalue context on
+the subroutine. This would prevent lvalue methods from returning certain
+values.
+
+=item *
+
+Lvalue sub calls that are not determined to be such at compile time
+(C<&$name> or &{"name"}) are no longer exempt from strict refs if they
+occur in the last statement of an lvalue subroutine [perl #102486].
+
+=item *
+
+Sub calls whose subs are not visible at compile time, if
+they occurred in the last statement of an lvalue subroutine,
+would reject non-lvalue subroutines and die with "Can't modify non-lvalue
+subroutine call" [perl #102486].
+
+Non-lvalue sub calls whose subs I<are> visible at compile time exhibited
+the opposite bug. If the call occurred in the last statement of an lvalue
+subroutine, there would be no error when the lvalue sub was called in
+lvalue context. Perl would blindly assign to the temporary value returned
+by the non-lvalue subroutine.
+
+=item *
+
+C<AUTOLOAD> routines used to take precedence over the actual sub being
+called (i.e., when autoloading wasn't needed), for sub calls in lvalue or
+potential lvalue context, if the subroutine was not visible at compile
+time.
+
+=item *
+
+Applying the C<:lvalue> attribute to an XSUB or to an aliased subroutine
+stub with C<< sub foo :lvalue; >> syntax stopped working in Perl 5.12.
+This has been fixed.
+
+=item *
+
+Applying the :lvalue attribute to subroutine that is already defined does
+not work properly, as the attribute changes the way the sub is compiled.
+Hence, Perl 5.12 began warning when an attempt is made to apply the
+attribute to an already defined sub. In such cases, the attribute is
+discarded.
+
+But the change in 5.12 missed the case where custom attributes are also
+present: that case still silently and ineffectively applied the attribute.
+That omission has now been corrected. C<sub foo :lvalue :Whatever> (when
+C<foo> is already defined) now warns about the :lvalue attribute, and does
+not apply it.
+
+=item *
+
+A bug affecting lvalue context propagation through nested lvalue subroutine
+calls has been fixed. Previously, returning a value in nested rvalue
+context would be treated as lvalue context by the inner subroutine call,
+resulting in some values (such as read-only values) being rejected.
+
+=back
+
+=head2 Overloading
+
+=over
+
+=item *
+
+Arithmetic assignment (C<$left += $right>) involving overloaded objects
+that rely on the 'nomethod' override no longer segfault when the left
+operand is not overloaded.
+
+=item *
+
+Errors that occur when methods cannot be found during overloading now
+mention the correct package name, as they did in 5.8.x, instead of
+erroneously mentioning the "overload" package, as they have since 5.10.0.
+
+=item *
+
+Undefining C<%overload::> no longer causes a crash.
+
+=back
+
+=head2 Prototypes of built-in keywords
+
+=over
+
+=item *
+
+The C<prototype> function no longer dies for the C<__FILE__>, C<__LINE__>
+and C<__PACKAGE__> directives. It now returns an empty-string prototype
+for them, because they are syntactically indistinguishable from nullary
+functions like C<time>.
+
+=item *
+
+C<prototype> now returns C<undef> for all overridable infix operators,
+such as C<eq>, which are not callable in any way resembling functions.
+It used to return incorrect prototypes for some and die for others
+[perl #94984].
+
+=item *
+
+The prototypes of several built-in functions--C<getprotobynumber>, C<lock>,
+C<not> and C<select>--have been corrected, or at least are now closer to
+reality than before.
+
+=back
+
+=head2 Regular expressions
+
+=for comment Is it possible to merge some of these items?
+
+=over 4
+
+=item *
+
+C</[[:ascii:]]/> and C</[[:blank:]]/> now use locale rules under
+C<use locale> when the platform supports that. Previously, they used
+the platform's native character set.
+
+=item *
+
+C<m/[[:ascii:]]/i> and C</\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.
+
+=item *
+
+C</.*/g> would sometimes refuse to match at the end of a string that ends
+with "\n". This has been fixed [perl #109206].
+
+=item *
+
+Starting with 5.12.0, Perl used to get its internal bookkeeping muddled up
+after assigning C<${ qr// }> to a hash element and locking it with
+L<Hash::Util>. This could result in double frees, crashes or erratic
+behaviour.
+
+=item *
+
+The new (in 5.14.0) regular expression modifier C</a> when repeated like
+C</aa> forbids the characters outside the ASCII range that match
+characters inside that range from matching under C</i>. This did not
+work under some circumstances, all involving alternation, such as:
+
+ "\N{KELVIN SIGN}" =~ /k|foo/iaa;
+
+succeeded inappropriately. This is now fixed.
+
+=item *
+
+5.14.0 introduced some memory leaks in regular expression character
+classes such as C<[\w\s]>, which have now been fixed. (5.14.1)
+
+=item *
+
+An edge case in regular expression matching could potentially loop.
+This happened only under C</i> in bracketed character classes that have
+characters with multi-character folds, and the target string to match
+against includes the first portion of the fold, followed by another
+character that has a multi-character fold that begins with the remaining
+portion of the fold, plus some more.
+
+ "s\N{U+DF}" =~ /[\x{DF}foo]/i
+
+is one such case. C<\xDF> folds to C<"ss">. (5.14.1)
+
+=item *
+
+A few characters in regular expression pattern matches did not
+match correctly in some circumstances, all involving C</i>. The
+affected characters are:
+COMBINING GREEK YPOGEGRAMMENI,
+GREEK CAPITAL LETTER IOTA,
+GREEK CAPITAL LETTER UPSILON,
+GREEK PROSGEGRAMMENI,
+GREEK SMALL LETTER IOTA WITH DIALYTIKA AND OXIA,
+GREEK SMALL LETTER IOTA WITH DIALYTIKA AND TONOS,
+GREEK SMALL LETTER UPSILON WITH DIALYTIKA AND OXIA,
+GREEK SMALL LETTER UPSILON WITH DIALYTIKA AND TONOS,
+LATIN SMALL LETTER LONG S,
+LATIN SMALL LIGATURE LONG S T,
+and
+LATIN SMALL LIGATURE ST.
+
+=item *
+
+A memory leak regression in regular expression compilation
+under threading has been fixed.
+
+=item *
+
+A regression introduced in 5.13.6 has
+been 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.
+
+=item *
+
+Three problematic Unicode characters now work better in regex pattern matching under C</i>
+
+In the past, three Unicode characters:
+LATIN SMALL LETTER SHARP S,
+GREEK SMALL LETTER IOTA WITH DIALYTIKA AND TONOS,
+and
+GREEK SMALL LETTER UPSILON WITH DIALYTIKA AND TONOS,
+along with the sequences that they fold to
+(including "ss" in the case of LATIN SMALL LETTER SHARP S),
+did not properly match under C</i>. 5.14.0 fixed some of these cases,
+but introduced others, including a panic when one of the characters or
+sequences was used in the C<(?(DEFINE)> regular expression predicate.
+The known bugs that were introduced in 5.14 have now been fixed; as well
+as some other edge cases that have never worked until now. All these
+involve using the characters and sequences outside bracketed character
+classes under C</i>. This closes [perl #98546].
+
+There remain known problems when using certain characters with
+multi-character folds inside bracketed character classes, including such
+constructs as C<qr/[\N{LATIN SMALL LETTER SHARP}a-z]/i>. These
+remaining bugs are addressed in [perl #89774].
+
+=item *
+
+RT #78266: The regex engine has been leaking memory when accessing
+named captures that weren't matched as part of a regex ever since 5.10
+when they were introduced, e.g. this would consume over a hundred MB of
+memory:
+
+ for (1..10_000_000) {
+ if ("foo" =~ /(foo|(?<capture>bar))?/) {
+ my $capture = $+{capture}
+ }
+ }
+ system "ps -o rss $$"'
+
+=item *
+
+In 5.14, C</[[:lower:]]/i> and C</[[:upper:]]/i> no longer matched the
+opposite case. This has been fixed [perl #101970].
+
+=item *
+
+A regular expression match with an overloaded object on the right-hand side
+would in some cases stringify the object too many times.
+
+=item *
+
+A regression has been fixed that was introduced in 5.14, in C</i>
+regular expression matching, in which a match improperly fails if the
+pattern is in UTF-8, the target string is not, and a Latin-1 character
+precedes a character in the string that should match the pattern.
+[perl #101710]
+
+=item *
+
+In case-insensitive regular expression pattern matching, no longer on
+UTF-8 encoded strings does the scan for the start of match only look at
+the first possible position. This caused matches such as
+C<"f\x{FB00}" =~ /ff/i> to fail.
+
+=item *
+
+The regexp optimiser no longer crashes on debugging builds when merging
+fixed-string nodes with inconvenient contents.
+
+=item *
+
+A panic involving the combination of the regular expression modifiers
+C</aa> and the C<\b> escape sequence introduced in 5.14.0 has been
+fixed [perl #95964].
+
+=item *
+
+The combination of the regular expression modifiers C</aa> and the C<\b>
+and C<\B> escape sequences did not work properly on UTF-8 encoded
+strings. All non-ASCII characters under C</aa> should be treated as
+non-word characters, but what was happening was that Unicode rules were
+used to determine wordness/non-wordness for non-ASCII characters. This
+is now fixed [perl #95968].
+
+=item *
+
+C<< (?foo: ...) >> no longer loses passed in character set.
+
+=item *
+
+The trie optimisation used to have problems with alternations containing
+an empty C<(?:)>, causing C<< "x" =~ /\A(?>(?:(?:)A|B|C?x))\z/ >> not to
+match, whereas it should [perl #111842].
+
+=item *
+
+Use of lexical (C<my>) variables in code blocks embedded in regular
+expressions will no longer result in memory corruption or crashes.
+
+Nevertheless, these code blocks are still experimental, as there are still
+problems with the wrong variables being closed over (in loops for instance)
+and with abnormal exiting (e.g., C<die>) causing memory corruption.
+
+=item *
+
+The C<\h>, C<\H>, C<\v> and C<\V> regular expression metacharacters used to
+cause a panic error message when attempting to match at the end of the
+string [perl #96354].
+
+=item *
+
+The abbreviations for four C1 control characters C<MW> C<PM>, C<RI>, and
+C<ST> were previously unrecognized by C<\N{}>, vianame(), and
+string_vianame().
+
+=item *
+
+Mentioning a variable named "&" other than C<$&> (i.e., C<@&> or C<%&>) no
+longer stops C<$&> from working. The same applies to variables named "'"
+and "`" [perl #24237].
+
+=item *
+
+Creating a C<UNIVERSAL::AUTOLOAD> sub no longer stops C<%+>, C<%-> and
+C<%!> from working some of the time [perl #105024].
+
+=back
+
+=head2 Smartmatching
+
+=over
+
+=item *
+
+C<~~> now correctly handles the precedence of Any~~Object, and is not tricked
+by an overloaded object on the left-hand side.
+
+=item *
+
+In Perl 5.14.0, C<$tainted ~~ @array> stopped working properly. Sometimes
+it would erroneously fail (when C<$tainted> contained a string that occurs
+in the array I<after> the first element) or erroneously succeed (when
+C<undef> occurred after the first element) [perl #93590].
+
+=back
+
+=head2 The C<sort> operator
+
+=over
+
+=item *
+
+C<sort> was not treating C<sub {}> and C<sub {()}> as equivalent when
+such a sub was provided as the comparison routine. It used to croak on
+C<sub {()}>.
+
+=item *
+
+C<sort> now works once more with custom sort routines that are XSUBs. It
+stopped working in 5.10.0.
+
+=item *
+
+C<sort> with a constant for a custom sort routine, although it produces
+unsorted results, no longer crashes. It started crashing in 5.10.0.
+
+=item *
+
+Warnings emitted by C<sort> when a custom comparison routine returns a
+non-numeric value now contain "in sort" and show the line number of the
+C<sort> operator, rather than the last line of the comparison routine. The
+warnings also occur now only if warnings are enabled in the scope where
+C<sort> occurs. Previously the warnings would occur if enabled in the
+comparison routine's scope.
+
+=item *
+
+C<< sort { $a <=> $b } >>, which is optimised internally, now produces
+"uninitialized" warnings for NaNs (not-a-number values), since C<< <=> >>
+returns C<undef> for those. This brings it in line with
+S<C<< sort { 1; $a <=> $b } >>> and other more complex cases, which are not
+optimised [perl #94390].
+
+=back
+
+=head2 The C<substr> operator
+
+=over
+
+=item *
+
+Tied (and otherwise magical) variables are no longer exempt from the
+"Attempt to use reference as lvalue in substr" warning.
+
+=item *
+
+That warning now occurs when the returned lvalue is assigned to, not
+when C<substr> itself is called. This only makes a difference if the
+return value of C<substr> is referenced and assigned to later.
+
+=item *
+
+Passing a substring of a read-only value or a typeglob to a function
+(potential lvalue context) no longer causes an immediate "Can't coerce"
+or "Modification of a read-only value" error. That error only occurs
+if and when the value passed is assigned to.
+
+The same thing happens with the "substr outside of string" error. If
+the lvalue is only read, not written to, it is now just a warning, as
+with rvalue C<substr>.
+
+=item *
+
+C<substr> assignments no longer call FETCH twice if the first argument
+is a tied variable, just once.
+
+=back
+
+=head2 Support for embedded nulls
+
+Some parts of Perl did not work correctly with nulls (C<chr 0>) embedded in
+strings. That meant that, for instance, C<< $m = "a\0b"; foo->$m >> would
+call the "a" method, instead of the actual method name contained in $m.
+These parts of perl have been fixed to support nulls:
+
+=over
+
+=item *
+
+Method names
+
+=item *
+
+Typeglob names (including filehandle and subroutine names)
+
+=item *
+
+Package names, including the return value of C<ref()>
+
+=item *
+
+Typeglob elements (C<*foo{"THING\0stuff"}>)
+
+=item *
+
+Signal names
+
+=item *
+
+Various warnings and error messages that mention variable names or values,
+methods, etc.
+
+=back
+
+One side effect of these changes is that blessing into "\0" no longer
+causes C<ref()> to return false.
+
+=head2 Threading bugs
+
+=over
+
+=item *
+
+Typeglobs returned from threads are no longer cloned if the parent thread
+already has a glob with the same name. This means that returned
+subroutines will now assign to the right package variables [perl #107366].
+
+=item *
+
+Some cases of threads crashing due to memory allocation during cloning have
+been fixed [perl #90006].
+
+=item *
+
+Thread joining would sometimes emit "Attempt to free unreferenced scalar"
+warnings if C<caller> had been used from the C<DB> package prior to thread
+creation [perl #98092].
+
+=item *
+
+Locking a subroutine (via C<lock &sub>) is no longer a compile-time error
+for regular subs. For lvalue subroutines, it no longer tries to return the
+sub as a scalar, resulting in strange side effects like C<ref \$_>
+returning "CODE" in some instances.
+
+C<lock &sub> is now a run-time error if L<threads::shared> is loaded (a
+no-op otherwise), but that may be rectified in a future version.
+
+=back
+
+=head2 Tied variables
+
+=over
+
+=item *
+
+Various cases in which FETCH was being ignored or called too many times
+have been fixed:
+
+=over
+
+=item *
+
+C<PerlIO::get_layers> [perl #97956]
+
+=item *
+
+C<$tied =~ y/a/b/>, C<chop $tied> and C<chomp $tied> when $tied holds a
+reference.
+
+=item *
+
+When calling C<local $_> [perl #105912]
+
+=item *
+
+Four-argument C<select>
+
+=item *
+
+A tied buffer passed to C<sysread>
+
+=item *
+
+C<< $tied .= <> >>
+
+=item *
+
+Three-argument C<open>, the third being a tied file handle
+(as in C<< open $fh, ">&", $tied >>)
+
+=item *
+
+C<sort> with a reference to a tied glob for the comparison routine.
+
+=item *
+
+C<..> and C<...> in list context [perl #53554].
+
+=item *
+
+C<${$tied}>, C<@{$tied}>, C<%{$tied}> and C<*{$tied}> where the tied
+variable returns a string (C<&{}> was unaffected)
+
+=item *
+
+C<defined ${ $tied_variable }>
+
+=item *
+
+Various functions that take a filehandle argument in rvalue context
+(C<close>, C<readline>, etc.) [perl #97482]
+
+=item *
+
+Some cases of dereferencing a complex expression, such as
+C<${ (), $tied } = 1>, used to call C<FETCH> multiple times, but now call
+it once.
+
+=item *
+
+C<$tied-E<gt>method> where $tied returns a package name--even resulting in
+a failure to call the method, due to memory corruption
+
+=item *
+
+Assignments like C<*$tied = \&{"..."}> and C<*glob = $tied>
+
+=item *
+
+C<chdir>, C<chmod>, C<chown>, C<utime>, C<truncate>, C<stat>, C<lstat> and
+the filetest ops (C<-r>, C<-x>, etc.)
+
+=back
+
+=item *
+
+C<caller> sets C<@DB::args> to the subroutine arguments when called from
+the DB package. It used to crash when doing so if C<@DB::args> happened to
+be tied. Now it croaks instead.
+
+=item *
+
+Tying an element of %ENV or C<%^H> and then deleting that element would
+result in a call to the tie object's DELETE method, even though tying the
+element itself is supposed to be equivalent to tying a scalar (the element
+is, of course, a scalar) [perl #67490].
+
+=item *
-XXX Generate this with:
+When Perl autovivifies an element of a tied array or hash (which entails
+calling STORE with a new reference), it now calls FETCH immediately after
+the STORE, instead of assuming that FETCH would have returned the same
+reference. This can make it easier to implement tied objects [perl #35865, #43011].
+
+=item *
+
+Four-argument C<select> no longer produces its "Non-string passed as
+bitmask" warning on tied or tainted variables that are strings.
+
+=item *
+
+Localising a tied scalar that returns a typeglob no longer stops it from
+being tied till the end of the scope.
+
+=item *
+
+Attempting to C<goto> out of a tied handle method used to cause memory
+corruption or crashes. Now it produces an error message instead
+[perl #8611].
+
+=item *
+
+A bug has been fixed that occurs when a tied variable is used as a
+subroutine reference: if the last thing assigned to or returned from the
+variable was a reference or typeglob, the C<\&$tied> could either crash or
+return the wrong subroutine. The reference case is a regression introduced
+in Perl 5.10.0. For typeglobs, it has probably never worked till now.
+
+=back
+
+=head2 Version objects and vstrings
+
+=over
+
+=item *
+
+The bitwise complement operator (and possibly other operators, too) when
+passed a vstring would leave vstring magic attached to the return value,
+even though the string had changed. This meant that
+C<< version->new(~v1.2.3) >> would create a version looking like "v1.2.3"
+even though the string passed to C<< version->new >> was actually
+"\376\375\374". This also caused L<B::Deparse> to deparse C<~v1.2.3>
+incorrectly, without the C<~> [perl #29070].
+
+=item *
+
+Assigning a vstring to a magic (e.g., tied, C<$!>) variable and then
+assigning something else used to blow away all the magic. This meant that
+tied variables would come undone, C<$!> would stop getting updated on
+failed system calls, C<$|> would stop setting autoflush, and other
+mischief would take place. This has been fixed.
+
+=item *
+
+C<< version->new("version") >> and C<printf "%vd", "version"> no longer
+crash [perl #102586].
+
+=item *
+
+Version comparisons, such as those that happen implicitly with C<use
+v5.43>, no longer cause locale settings to change [perl #105784].
+
+=item *
+
+Version objects no longer cause memory leaks in boolean context
+[perl #109762].
+
+=back
+
+=head2 Warnings, redefinition
+
+=over
+
+=item *
+
+Subroutines from the C<autouse> namespace are once more exempt from
+redefinition warnings. This used to work in 5.005, but was broken in
+5.6 for most subroutines. For subs created via XS that redefine
+subroutines from the C<autouse> package, this stopped working in 5.10.
+
+=item *
+
+New XSUBs now produce redefinition warnings if they overwrite existing
+subs, as they did in 5.8.x. (The C<autouse> logic was reversed in
+5.10-14. Only subroutines from the C<autouse> namespace would warn
+when clobbered.)
+
+=item *
+
+C<newCONSTSUB> used to use compile-time warning hints, instead of
+run-time hints. The following code should never produce a redefinition
+warning, but it used to, if C<newCONSTSUB> redefined an existing
+subroutine:
+
+ use warnings;
+ BEGIN {
+ no warnings;
+ some_XS_function_that_calls_new_CONSTSUB();
+ }
+
+=item *
+
+Redefinition warnings for constant subroutines are on by default (what
+are known as severe warnings in L<perldiag>). This was only the case
+when it was a glob assignment or declaration of a Perl subroutine that
+caused the warning. If the creation of XSUBs triggered the warning, it
+was not a default warning. This has been corrected.
+
+=item *
+
+The internal check to see whether a redefinition warning should occur
+used to emit "uninitialized" warnings in cases like this:
+
+ use warnings "uninitialized";
+ use constant {u => undef, v => undef};
+ sub foo(){u}
+ sub foo(){v}
+
+=back
+
+=head2 Warnings, "Uninitialized"
+
+=over
+
+=item *
+
+Various functions that take a filehandle argument in rvalue context
+(C<close>, C<readline>, etc.) used to warn twice for an undefined handle
+[perl #97482].
+
+=item *
+
+C<dbmopen> now only warns once, rather than three times, if the mode
+argument is C<undef> [perl #90064].
+
+=item *
+
+The C<+=> operator does not usually warn when the left-hand side is
+C<undef>, but it was doing so for tied variables. This has been fixed
+[perl #44895].
+
+=item *
+
+A bug fix in Perl 5.14 introduced a new bug, causing "uninitialized"
+warnings to report the wrong variable if the operator in question had
+two operands and one was C<%{...}> or C<@{...}>. This has been fixed
+[perl #103766].
+
+=item *
+
+C<..> and C<...> in list context now mention the name of the variable in
+"uninitialized" warnings for string (as opposed to numeric) ranges.
+
+=back
+
+=head2 Weak references
+
+=over
+
+=item *
+
+Weakening the first argument to an automatically-invoked C<DESTROY> method
+could result in erroneous "DESTROY created new reference" errors or
+crashes. Now it is an error to weaken a read-only reference.
+
+=item *
+
+Weak references to lexical hashes going out of scope were not going stale
+(becoming undefined), but continued to point to the hash.
+
+=item *
+
+Weak references to lexical variables going out of scope are now broken
+before any magical methods (e.g., DESTROY on a tie object) are called.
+This prevents such methods from modifying the variable that will be seen
+the next time the scope is entered.
+
+=item *
+
+Creating a weak reference to an @ISA array or accessing the array index
+(C<$#ISA>) could result in confused internal bookkeeping for elements
+subsequently added to the @ISA array. For instance, creating a weak
+reference to the element itself could push that weak reference on to @ISA;
+and elements added after use of C<$#ISA> would be ignored by method lookup
+[perl #85670].
+
+=back
+
+=head2 Other notable fixes
+
+=over
+
+=item *
+
+C<quotemeta> now quotes consistently the same non-ASCII characters under
+C<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 L<perlunicode/The "Unicode Bug">. [perl #77654].
+
+Which of these code points is quoted has changed, based on Unicode's
+recommendations. See L<perlfunc/quotemeta> for details.
+
+=item *
+
+When one writes C<open foo || die>, which used to work in Perl 4, a
+"Precedence problem" warning is produced. This warning used erroneously to
+apply to fully-qualified bareword handle names not followed by C<||>. This
+has been corrected.
+
+=item *
+
+After package aliasing (C<*foo:: = *bar::>), C<select> with 0 or 1 argument
+would sometimes return a name that could not be used to refer to the
+filehandle, or sometimes it would return C<undef> even when a filehandle
+was selected. Now it returns a typeglob reference in such cases.
+
+=item *
+
+C<PerlIO::get_layers> no longer ignores some arguments that it thinks are
+numeric, while treating others as filehandle names. It is now consistent
+for flat scalars (i.e., not references).
+
+=item *
+
+Unrecognised switches on C<#!> line
+
+If a switch, such as B<-x>, that cannot occur on the C<#!> line is used
+there, perl dies with "Can't emulate...".
+
+It used to produce the same message for switches that perl did not
+recognise at all, whether on the command line or the C<#!> line.
+
+Now it produces the "Unrecognized switch" error message [perl #104288].
+
+=item *
+
+C<system> now temporarily blocks the SIGCHLD signal handler, to prevent the
+signal handler from stealing the exit status [perl #105700].
+
+=item *
+
+The %n formatting code for C<printf> and C<sprintf>, which causes the number
+of characters to be assigned to the next argument, now actually
+assigns the number of characters, instead of the number of bytes.
+
+It also works now with special lvalue functions like C<substr> and with
+nonexistent hash and array elements [perl #3471, #103492].
+
+=item *
+
+Perl skips copying values returned from a subroutine, for the sake of
+speed, if doing so would make no observable difference. Due to faulty
+logic, this would happen with the
+result of C<delete>, C<shift> or C<splice>, even if the result was
+referenced elsewhere. It also did so with tied variables about to be freed
+[perl #91844, #95548].
+
+=item *
+
+C<utf8::decode> now refuses to modify read-only scalars [perl #91850].
+
+=item *
+
+Freeing $_ inside a C<grep> or C<map> block, a code block embedded in a
+regular expression, or an @INC filter (a subroutine returned by a
+subroutine in @INC) used to result in double frees or crashes
+[perl #91880, #92254, #92256].
+
+=item *
+
+C<eval> returns C<undef> in scalar context or an empty list in list
+context when there is a run-time error. When C<eval> was passed a
+string in list context and a syntax error occurred, it used to return a
+list containing a single undefined element. Now it returns an empty
+list in list context for all errors [perl #80630].
+
+=item *
+
+C<goto &func> no longer crashes, but produces an error message, when
+the unwinding of the current subroutine's scope fires a destructor that
+undefines the subroutine being "goneto" [perl #99850].
+
+=item *
+
+Perl now holds an extra reference count on the package that code is
+currently compiling in. This means that the following code no longer
+crashes [perl #101486]:
+
+ package Foo;
+ BEGIN {*Foo:: = *Bar::}
+ sub foo;
+
+=item *
+
+The C<x> repetition operator no longer crashes on 64-bit builds with large
+repeat counts [perl #94560].
+
+=item *
+
+Calling C<require> on an implicit C<$_> when C<*CORE::GLOBAL::require> has
+been overridden does not segfault anymore, and C<$_> is now passed to the
+overriding subroutine [perl #78260].
+
+=item *
+
+C<use> and C<require> are no longer affected by the I/O layers active in
+the caller's scope (enabled by L<open.pm|open>) [perl #96008].
+
+=item *
+
+C<our $::é; $é> (which is invalid) no longer produces the "Compilation
+error at lib/utf8_heavy.pl..." error message, which it started emitting in
+5.10.0 [perl #99984].
+
+=item *
+
+On 64-bit systems, C<read()> now understands large string offsets beyond
+the 32-bit range.
+
+=item *
+
+Errors that occur when processing subroutine attributes no longer cause the
+subroutine's op tree to leak.
+
+=item *
+
+Passing the same constant subroutine to both C<index> and C<formline> no
+longer causes one or the other to fail [perl #89218]. (5.14.1)
+
+=item *
+
+List assignment to lexical variables declared with attributes in the same
+statement (C<my ($x,@y) : blimp = (72,94)>) stopped working in Perl 5.8.0.
+It has now been fixed.
+
+=item *
+
+Perl 5.10.0 introduced some faulty logic that made "U*" in the middle of
+a pack template equivalent to "U0" if the input string was empty. This has
+been fixed [perl #90160].
+
+=item *
+
+Destructors on objects were not called during global destruction on objects
+that were not referenced by any scalars. This could happen if an array
+element were blessed (e.g., C<bless \$a[0]>) or if a closure referenced a
+blessed variable (C<bless \my @a; sub foo { @a }>).
+
+Now there is an extra pass during global destruction to fire destructors on
+any objects that might be left after the usual passes that check for
+objects referenced by scalars [perl #36347].
+
+=item *
+
+Fixed a case where it was possible that a freed buffer may have been read
+from when parsing a here document [perl #90128]. (5.14.1)
+
+=item *
+
+C<each(I<ARRAY>)> is now wrapped in C<defined(...)>, like C<each(I<HASH>)>,
+inside a C<while> condition [perl #90888].
+
+=item *
+
+A problem with context propagation when a C<do> block is an argument to
+C<return> has been fixed. It used to cause C<undef> to be returned in
+some cases of a C<return> inside an C<if> block which itself is followed by
+another C<return>.
+
+=item *
+
+Calling C<index> with a tainted constant no longer causes constants in
+subsequently compiled code to become tainted [perl #64804].
+
+=item *
+
+Infinite loops like C<1 while 1> used to stop C<strict 'subs'> mode from
+working for the rest of the block.t
+
+=item *
+
+For list assignments like C<($a,$b) = ($b,$a)>, Perl has to make a copy of
+the items on the right-hand side before assignment them to the left. For
+efficiency's sake, it assigns the values on the right straight to the items
+on the left if no one variable is mentioned on both sides, as in C<($a,$b) =
+($c,$d)>. The logic for determining when it can cheat was faulty, in that
+C<&&> and C<||> on the right-hand side could fool it. So C<($a,$b) =
+$some_true_value && ($b,$a)> would end up assigning the value of C<$b> to
+both scalars.
+
+=item *
+
+Perl no longer tries to apply lvalue context to the string in
+C<("string", $variable) ||= 1> (which used to be an error). Since the
+left-hand side of C<||=> is evaluated in scalar context, that's a scalar
+comma operator, which gives all but the last item void context. There is
+no such thing as void lvalue context, so it was a mistake for Perl to try
+to force it [perl #96942].
+
+=item *
+
+C<caller> no longer leaks memory when called from the DB package if
+C<@DB::args> was assigned to after the first call to C<caller>. L<Carp>
+was triggering this bug [perl #97010].
+
+=item *
+
+C<close> and similar filehandle functions, when called on built-in global
+variables (like C<$+>), used to die if the variable happened to hold the
+undefined value, instead of producing the usual "Use of uninitialized
+value" warning.
+
+=item *
+
+When autovivified file handles were introduced in Perl 5.6.0, C<readline>
+was inadvertently made to autovivify when called as C<readline($foo)> (but
+not as C<E<lt>$fooE<gt>>). It has now been fixed never to autovivify.
+
+=item *
+
+Calling an undefined anonymous subroutine (e.g., what $x holds after
+C<undef &{$x = sub{}}>) used to cause a "Not a CODE reference" error, which
+has been corrected to "Undefined subroutine called" [perl #71154].
+
+=item *
+
+Causing C<@DB::args> to be freed between uses of C<caller> no longer
+results in a crash [perl #93320].
+
+=item *
+
+C<setpgrp($foo)> used to be equivalent to C<($foo, setpgrp)>, because
+C<setpgrp> was ignoring its argument if there was just one. Now it is
+equivalent to C<setpgrp($foo,0)>.
+
+=item *
+
+C<shmread> was not setting the scalar flags correctly when reading from
+shared memory, causing the existing cached numeric representation in the
+scalar to persist [perl #98480].
+
+=item *
+
+C<++> and C<--> now work on copies of globs, instead of dying.
+
+=item *
+
+C<splice()> doesn't warn when truncating
+
+You can now limit the size of an array using C<splice(@a,MAX_LEN)> without
+worrying about warnings.
+
+=item *
+
+C<< $$ >> is no longer tainted. Since this value comes directly from
+C<< getpid() >>, it is always safe.
+
+=item *
+
+The parser no longer leaks a filehandle if STDIN was closed before parsing
+started [perl #37033].
+
+=item *
+
+C<< die; >> with a non-reference, non-string, or magical (e.g., tainted)
+value in $@ now properly propagates that value [perl #111654].
+
+=back
+
+=head1 Known Problems
+
+=over 4
+
+=item *
+
+On Solaris, we have two kinds of failure.
+
+If F<make> is Sun's F<make≥>, we get an error about a badly formed macro
+assignment in the F<Makefile>. That happens when F<./Configure> tries to
+make depends. F<Configure> then exits 0, but further F<make>-ing fails.
+
+If F<make> is F<gmake>, F<Configure> completes, then we get errors related
+to F</usr/include/stdbool.h>
+
+=item *
+
+The following CPAN modules have test failures with perl 5.16. Patches have
+been submitted for all of these, so hopefully there will be new releases
+soon:
+
+=over
+
+=item *
+
+L<Date::Pcalc> version 6.1
+
+=item *
+
+L<Module::CPANTS::Analyse> version 0.85
+
+This fails due to problems in L<Module::Find> 0.10 and L<File::MMagic>
+1.27.
+
+=item *
+
+L<PerlIO::Util> version 0.72
+
+=back
+
+=back
+
+=head1 Acknowledgements
- perl Porting/acknowledgements.pl v5.15.7..HEAD
+Perl 5.16.0 represents approximately 12 months of development since Perl
+5.14.0 and contains approximately 590,000 lines of changes across 2,500
+files from 137 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 5.14.1:
+
+Aaron Crane, Abhijit Menon-Sen, Abigail, Alan Haggai Alavi, Alberto
+Simões, Alexandr Ciornii, Andreas König, Andy Dougherty, Aristotle
+Pagaltzis, Bo Johansson, Bo Lindbergh, brian d foy, Brian Fraser, Brian
+Greenfield, Carl Hayter, Chas. Owens, Chia-liang Kao, Chip Salzenberg,
+Chris 'BinGOs' Williams, Christian Hansen, Christopher J. Madsen,
+chromatic, Claes Jacobsson, Claudio Ramirez, Craig A. Berry, Damian
+Conway, Daniel Kahn Gillmor, Darin McBride, Dave Rolsky, David Cantrell,
+David Golden, David Leadbeater, David Mitchell, Dee Newcum, Dennis
+Kaarsemaker, Dominic Hargreaves, Douglas Christopher Wilson, Eric Brine,
+Father Chrysostomos, Florian Ragwitz, Frederic Briere, George Greer,
+Gerard Goossen, Gisle Aas, H.Merijn Brand, Hojung Youn, Ian Goodacre,
+James E Keenan, Jan Dubois, Jerry D. Hedden, Jesse Luehrs, Jesse
+Vincent, Jilles Tjoelker, Jim Cromie, Jim Meyering, Joel Berger, Johan
+Vromans, Johannes Plunien, John Hawkinson, John P. Linderman, John
+Peacock, Joshua ben Jore, Juerd Waalboer, Karl Williamson, Karthik
+Rajagopalan, Keith Thompson, Kevin J. Woolley, Kevin Ryde, Laurent
+Dami, Leo Lapworth, Leon Brocard, Leon Timmermans, Louis Strous, Lukas
+Mai, Marc Green, Marcel Grünauer, Mark A. Stratman, Mark Dootson, Mark
+Jason Dominus, Martin Hasch, Matthew Horsfall, Max Maischein, Michael G
+Schwern, Michael Witten, Mike Sheldrake, Moritz Lenz, Nicholas Clark,
+Niko Tyni, Nuno Carvalho, Pau Amma, Paul Evans, Paul Green, Paul
+Johnson, Perlover, Peter John Acklam, Peter Martini, Peter Scott, Phil
+Monsen, Pino Toscano, Rafael Garcia-Suarez, Rainer Tammer, Reini Urban,
+Ricardo Signes, Robin Barker, Rodolfo Carvalho, Salvador Fandiño, Sam
+Kimbrel, Samuel Thibault, Shawn M Moore, Shigeya Suzuki, Shlomi Fish,
+Sisyphus, Slaven Rezic, Spiros Denaxas, Steffen Müller, Steffen
+Schwigon, Stephen Bennett, Stephen Oberholtzer, Stevan Little, Steve
+Hay, Steve Peters, Thomas Sibley, Thorsten Glaser, Timothe Litt, Todd
+Rinaldo, Tom Christiansen, Tom Hukins, Tony Cook, Vadim Konovalov,
+Vincent Pit, Vladimir Timofeev, Walt Mankowski, Yves Orton, Zefram,
+Zsbán Ambrus, 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 F<AUTHORS> file in the Perl source distribution.
=head1 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.
+bug database at L<http://rt.perl.org/perlbug/>. 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
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.
+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.
=head1 SEE ALSO
https://perl5.git.perl.org / perl5.git / blobdiff