=head2 C<no re> covers more and is lexical
-Previously running C<no re> would only turn off a few things. Now it
+Previously running C<no re> would turn off only a few things. Now it
turns off all the enabled things. For example, previously, you
couldn't turn off debugging, once enabled, inside the same block.
=head2 Non-Capturing Regular Expression Flag
Regular expressions now support a C</n> flag that disables capturing
-and filling in C<$1>, C<$2>, etc... inside of groups:
+and filling in C<$1>, C<$2>, etc inside of groups:
"hello" =~ /(hi|hello)/n; # $1 is not set
=head2 C<use re 'strict'>
This applies stricter syntax rules to regular expression patterns
-compiled within its scope, which hopefully will alert you to typos and
+compiled within its scope. This will hopefully alert you to typos and
other unintentional behavior that backwards-compatibility issues prevent
-us from doing in normal regular expression compilations. Because the
+us from reporting in normal regular expression compilations. Because the
behavior of this is subject to change in future Perl releases as we gain
-experience, using this pragma will raise a category
-C<experimental::re_strict> warning.
+experience, using this pragma will raise a warning of category
+C<experimental::re_strict>.
See L<'strict' in re|re/'strict' mode>.
-=head2 C<qr/foo/x> now ignores any Unicode pattern white space
-
-The C</x> regular expression modifier allows the pattern to contain
-white space and comments, both of which are ignored, for improved
-readability. Until now, not all the white space characters that Unicode
-designates for this purpose were handled. The additional ones now
-recognized are
-U+0085 NEXT LINE,
-U+200E LEFT-TO-RIGHT MARK,
-U+200F RIGHT-TO-LEFT MARK,
-U+2028 LINE SEPARATOR,
-and
-U+2029 PARAGRAPH SEPARATOR.
-
=head2 Unicode 7.0 (with correction) is now supported
For details on what is in this release, see
and
C<int_p_sign_posn>.
-=head2 Better heuristics on older platforms for determining locale UTF8ness
+=head2 Better heuristics on older platforms for determining locale UTF-8ness
On platforms that implement neither the C99 standard nor the POSIX 2001
-standard, determining if the current locale is UTF8 or not depends on
+standard, determining if the current locale is UTF-8 or not depends on
heuristics. These are improved in this release.
=head2 Aliasing via reference
\$c = \$d;
\&x = \&y;
-Or by using a backslash before a C<foreach> iterator variable, which is
+Aliasing can also be accomplished
+by using a backslash before a C<foreach> iterator variable; this is
perhaps the most useful idiom this feature provides:
foreach \%hash (@array_of_hash_refs) { ... }
C<prototype()> with no arguments now infers C<$_>.
L<[perl #123514]|https://rt.perl.org/Ticket/Display.html?id=123514>.
-=head2 New "const" subroutine attribute
+=head2 New C<:const> subroutine attribute
-The "const" attribute can be applied to an anonymous subroutine. It causes
-it to be executed immediately when it is cloned. Its value is captured and
-used to create a new constant subroutine that is returned. This feature is
-experimental. See L<perlsub/Constant Functions>.
+The C<const> attribute can be applied to an anonymous subroutine. It
+causes the new sub to be executed immediately whenever one is created
+(i.e. when the C<sub> expression is evaluated). Its value is captured
+and used to create a new constant subroutine that is returned. This
+feature is experimental. See L<perlsub/Constant Functions>.
=head2 C<fileno> now works on directory handles
=head2 Infinity and NaN (not-a-number) handling improved
-Floating point values are able to hold the special values infinity (also
--infinity), and NaN (not-a-number). Now we more robustly recognize and
-propagate the value in computations, and on output normalize them to C<Inf> and
-C<NaN>.
+Floating point values are able to hold the special values infinity, negative
+infinity, and NaN (not-a-number). Now we more robustly recognize and
+propagate the value in computations, and on output normalize them to C<Inf>,
+C<-Inf>, or C<NaN>.
See also the L<POSIX> enhancements.
As a completely new feature, hexadecimal floating point literals
(like C<0x1.23p-4>) are now supported, and they can be output with
-C<printf %a>.
+C<printf "%a">. See L<perldata/Scalar value constructors> for more
+details.
=head2 Packing infinity or not-a-number into a character is now fatal
=head2 Experimental C Backtrace API
-Perl now supports retrieving
+Perl now supports (via a C level API) retrieving
the C level backtrace (similar to what symbolic debuggers like gdb do).
The backtrace returns the stack trace of the C call frames,
The feature needs to be enabled with C<Configure -Dusecbacktrace>.
-Also included is a C API to retrieve backtraces.
-
See L<perlhacktips/"C backtrace"> for more information.
=head1 Security
=head2 Subroutine signatures moved before attributes
The experimental sub signatures feature, as introduced in 5.20, parsed
-signatures after attributes. In this release, the positioning has been
-moved such that signatures occur after the subroutine name (if any) and
-before the attribute list (if any).
+signatures after attributes. In this release, following feedback from users
+of the experimental feature, the positioning has been moved such that
+signatures occur after the subroutine name (if any) and before the attribute
+list (if any).
=head2 C<&> and C<\&> prototypes accepts only subs
-The C<&> prototype character now accepts only anonymous subs (C<sub {...}>)
-and things beginning with C<\&>. Formerly it erroneously also allowed
-C<undef> and references to array, hashes, and lists.
+The C<&> prototype character now accepts only anonymous subs (C<sub
+{...}>), things beginning with C<\&>, or an explicit C<undef>. Formerly
+it erroneously also allowed references to arrays, hashes, and lists.
L<[perl #4539]|https://rt.perl.org/Ticket/Display.html?id=4539>.
L<[perl #123062]|https://rt.perl.org/Ticket/Display.html?id=123062>.
+L<[perl #123062]|https://rt.perl.org/Ticket/Display.html?id=123475>.
-The C<\&> prototype was allowing subroutine calls, whereas now it only
-allows subroutines. C<&foo> is permitted. C<&foo()> and C<foo()> are not.
+In addition, the C<\&> prototype was allowing subroutine calls, whereas
+now it only allows subroutines: C<&foo> is still permitted as an argument,
+while C<&foo()> and C<foo()> no longer are.
L<[perl #77860]|https://rt.perl.org/Ticket/Display.html?id=77860>.
=head2 C<use encoding> is now lexical
=head2 List slices returning empty lists
-List slices return an empty list now only if the original list was empty
+List slices now return an empty list only if the original list was empty
(or if there are no indices). Formerly, a list slice would return an empty
-list if all indices fell outside the original list.
+list if all indices fell outside the original list; now it returns a list
+of undef values in that case.
L<[perl #114498]|https://rt.perl.org/Ticket/Display.html?id=114498>.
=head2 C<\N{}> with a sequence of multiple spaces is now a fatal error
+E.g. C<\N{TOO MANY SPACES}> or C<\N{TRAILING SPACE }>.
This has been deprecated since v5.18.
=head2 S<C<use UNIVERSAL '...'>> is now a fatal error
Importing functions from C<UNIVERSAL> has been deprecated since v5.12, and
-is now a fatal error. S<C<"use UNIVERSAL">> without any arguments is still
+is now a fatal error. S<C<use UNIVERSAL>> without any arguments is still
allowed.
=head2 In double-quotish C<\cI<X>>, I<X> must now be a printable ASCII character
These had been deprecated since v5.18.
-=head2 5 additional characters are treated as white space under C</x> in
-regex patterns (unless escaped)
+=head2 C<qr/foo/x> now ignores all Unicode pattern white space
+
+The C</x> regular expression modifier allows the pattern to contain
+white space and comments (both of which are ignored) for improved
+readability. Until now, not all the white space characters that Unicode
+designates for this purpose were handled. The additional ones now
+recognized are
+
+ U+0085 NEXT LINE
+ U+200E LEFT-TO-RIGHT MARK
+ U+200F RIGHT-TO-LEFT MARK
+ U+2028 LINE SEPARATOR
+ U+2029 PARAGRAPH SEPARATOR
The use of these characters with C</x> outside bracketed character
classes and when not preceded by a backslash has raised a deprecation
-warning since v5.18. Now they will be ignored. See L</"qr/foo/x">
-for the list of the five characters.
+warning since v5.18. Now they will be ignored.
-=head2 Comment lines within S<C<(?[ ])>> now are ended only by a C<\n>
+=head2 Comment lines within S<C<(?[ ])>> are now ended only by a C<\n>
S<C<(?[ ])>> is an experimental feature, introduced in v5.18. It operates
-as if C</x> is always enabled. But there was a difference, comment
+as if C</x> is always enabled. But there was a difference: comment
lines (following a C<#> character) were terminated by anything matching
C<\R> which includes all vertical whitespace, such as form feeds. For
consistency, this is now changed to match what terminates comment lines
names in some spots. This has issued a deprecation warning since Perl
5.000, and is no longer permitted.
-=head2 C<"$!"> text is now in English outside C<"use locale"> scope
+=head2 C<"$!"> text is now in English outside the scope of C<use locale>
Previously, the text, unlike almost everything else, always came out
based on the current underlying locale of the program. (Also affected
-on some systems is C<"$^E>".) For programs that are unprepared to
-handle locale, this can cause garbage text to be displayed. It's better
-to display text that is translatable via some tool than garbage text
-which is much harder to figure out.
+on some systems is C<"$^E">.) For programs that are unprepared to
+handle locale differences, this can cause garbage text to be displayed.
+It's better to display text that is translatable via some tool than
+garbage text which is much harder to figure out.
=head2 C<"$!"> text will be returned in UTF-8 when appropriate
that are set up to be locale-aware to properly output messages in the
user's native language. Code that needs to continue the 5.20 and
earlier behavior can do the stringification within the scopes of both
-S<C<'use bytes'>> and S<C<'use locale ":messages">>. No other Perl
+S<C<use bytes>> and S<C<use locale ":messages">>. No other Perl
operations will
be affected by locale; only C<$!> and C<$^E> stringification. The
-'bytes' pragma causes the UTF-8 flag to not be set, just as in previous
+C<bytes> pragma causes the UTF-8 flag to not be set, just as in previous
Perl releases. This resolves
L<[perl #112208]|https://rt.perl.org/Ticket/Display.html?id=112208>.
=head2 Support for C<?PATTERN?> without explicit operator has been removed
-Starting regular expressions matching only once directly with the
-question mark delimiter is now a syntax error, so that the question mark
-can be available for use in new operators. Write C<m?PATTERN?> instead,
-explicitly using the C<m> operator: the question mark delimiter still
-invokes match-once behaviour.
+The C<m?PATTERN?> construct, which allows matching a regex only once,
+previously had an alternative form that was written directly with a question
+mark delimiter, omitting the explicit C<m> operator. This usage has produced
+a deprecation warning since 5.14.0. It is now a syntax error, so that the
+question mark can be available for use in new operators.
=head2 C<defined(@array)> and C<defined(%hash)> are now fatal errors
=head2 Using a hash or an array as a reference are now fatal errors
-For example, C<%foo-E<gt>{"bar"}> now causes a fatal compilation
+For example, C<< %foo->{"bar"} >> now causes a fatal compilation
error. These have been deprecated since before v5.8, and have raised
deprecation warnings since then.
=head2 Changes to the C<*> prototype
The C<*> character in a subroutine's prototype used to allow barewords to take
-precedence over most, but not all subroutines. It was never consistent and
-exhibited buggy behaviour.
+precedence over most, but not all, subroutine names. It was never
+consistent and exhibited buggy behaviour.
Now it has been changed, so subroutines always take precedence over barewords,
which brings it into conformity with similarly prototyped built-in functions:
=head2 Setting C<${^ENCODING}> to anything but C<undef>
-This variable allows Perl scripts to be written in a non-ASCII,
-non-UTF-8 encoding. However, it affects all modules globally, leading
+This variable allows Perl scripts to be written in an encoding other than
+ASCII or UTF-8. However, it affects all modules globally, leading
to wrong answers and segmentation faults. New scripts should be written
in UTF-8; old scripts should be converted to UTF-8, which is easily done
-with the L<encoding> pragma.
-
-=head2 C<< /\C/ >> character class
-
-This character class, which matches a single byte, even if it appears
-in a multi-byte character has been deprecated. Matching single bytes
-in a multi-byte character breaks encapsulation, and can corrupt utf8
-strings.
+with the L<piconv> utility.
=head2 Use of non-graphic characters in single-character variable names
punctuation character or even invisible (a non-graphic). Perl v5.20
deprecated the ASCII-range controls as such a name. Now, all
non-graphic characters that formerly were allowed are deprecated.
-The practical effect of this occurs only when not under C<S<"use
-utf8">>, and affects just the C1 controls (code points 0x80 through
+The practical effect of this occurs only when not under C<S<use
+utf8>>, and affects just the C1 controls (code points 0x80 through
0xFF), NO-BREAK SPACE, and SOFT HYPHEN.
=head2 Inlining of C<sub () { $var }> with observable side-effects
In many cases Perl makes S<C<sub () { $var }>> into an inlinable constant
subroutine, capturing the value of C<$var> at the time the C<sub> expression
is evaluated. This can break the closure behaviour in those cases where
-C<$var> is subsequently modified. The subroutine won't return the new value.
+C<$var> is subsequently modified, since the subroutine won't return the
+changed value. (Note that this all only applies to anonymous subroutines
+with an empty prototype (C<sub ()>).)
This usage is now deprecated in those cases where the variable could be
modified elsewhere. Perl detects those cases and emits a deprecation
That is, now C<x> should only occur once in any string of contiguous
regular expression pattern modifiers. We do not believe there are any
occurrences of this in all of CPAN. This is in preparation for a future
-Perl release having C</xx> mean to allow white-space for readability in
+Perl release having C</xx> permit white-space for readability in
bracketed character classes (those enclosed in square brackets:
C<[...]>).
=head2 Making all warnings fatal is discouraged
The documentation for L<fatal warnings|warnings/Fatal Warnings> notes that
-C<< use warnings FATAL => 'all' >> is discouraged and provides stronger
+C<< use warnings FATAL => 'all' >> is discouraged, and provides stronger
language about the risks of fatal warnings in general.
=head1 Performance Enhancements
=item *
-If method and class names are known at compile time, hashes are precomputed
+If a method or class name is known at compile time, a hash is precomputed
to speed up run-time method lookup. Also, compound method names like
C<SUPER::new> are parsed at compile time, to save having to parse them at
run time.
context. If the right-hand argument is a constant 1, the repetition
operator disappears. If the right-hand argument is a constant 0, the whole
expression is optimised to the empty list, so long as the left-hand
-argument is a simple scalar or constant. C<(foo())x0> is not optimised.
+argument is a simple scalar or constant. (That is, C<(foo())x0> is not
+subject to this optimisation.)
=item *
=item *
-Assignment to lexical variables is often optimised away. For instance, in
-C<$lexical = chr $foo>, the C<chr> operator writes directly to the lexical
-variable instead of returning a value that gets copied. This optimisation
-has been extended to C<split>, C<x> and C<vec> on the right-hand side. It
-has also been made to work with state variable initialization.
-
-=item *
-
-In "C<\L>...", "C<\Q>...", etc., the extra "stringify" op is now optimised away,
-making these just as fast as C<lcfirst>, C<quotemeta>, etc.
+In C<"\L...">, C<"\Q...">, etc., the extra "stringify" op is now optimised
+away, making these just as fast as C<lcfirst>, C<quotemeta>, etc.
=item *
=item *
-C<length> is up to 20% faster for non-magical/non-tied scalars containing a
-string if it is a non-utf8 string or if is in scope of C<use bytes>.
+There is a performance improvement of up to 20% when C<length> is applied to
+a non-magical, non-tied string, and either C<use bytes> is in scope or the
+string doesn't use UTF-8 internally.
=item *
-Non-magical/non-tied scalars that contain only a floating point value and are
-on most Perl builds with 64 bit integers now use 8-32 less bytes of memory
-depending on OS.
+On most perl builds with 64-bit integers, memory usage for non-magical,
+non-tied scalars containing only a floating point value has been reduced
+by between 8 and 32 bytes, depending on OS.
=item *
-In C<@array = split>, the assignment can be optimized away with C<split>
-writing directly to the array. This optimisation was happening only for
-package arrays other than C<@_> and only
-sometimes. Now this optimisation happens
-almost all the time.
+In C<@array = split>, the assignment can be optimized away, so that C<split>
+writes directly to the array. This optimisation was happening only for
+package arrays other than C<@_>, and only sometimes. Now this
+optimisation happens almost all the time.
=item *
-C<join> is now subject to constant folding. Moreover, C<join> with a
-scalar or constant for the separator and a single-item list to join is
-simplified to a stringification. The separator doesn't even get evaluated.
+C<join> is now subject to constant folding. So for example
+C<join "-", "a", "b"> is converted at compile-time to C<"a-b">.
+Moreover, C<join> with a scalar or constant for the separator and a
+single-item list to join is simplified to a stringification, and the
+separator doesn't even get evaluated.
=item *
=item *
-Refactoring of C<< pp_tied >> and C<< pp_ref >> for small improvements.
-
-=item *
-
-Pathtools don't try to load XS on miniperl.
-
-=item *
-
-A typo fix reduces the size of the C<< OP >> structure.
-
-=item *
-
Hash lookups where the key is a constant are faster.
=item *
-Subroutines with an empty prototype and bodies containing just C<undef> are now
+Subroutines with an empty prototype and a body containing just C<undef> are now
eligible for inlining.
L<[perl #122728]|https://rt.perl.org/Ticket/Display.html?id=122728>
=item *
-Subroutines in packages no longer need to carry typeglobs around with them.
-Declaring a subroutine will now put a simple sub reference in the stash if
-possible, saving memory. The typeglobs still notionally exist, so accessing
-them will cause the subroutine reference to be upgraded to a typeglob. This
-optimization does not currently apply to XSUBs or exported subroutines, and
-method calls will undo it, since they cache things in typeglobs.
+Subroutines in packages no longer need to be stored in typeglobs:
+declaring a subroutine will now put a simple sub reference directly in the
+stash if possible, saving memory. The typeglob still notionally exists,
+so accessing it will cause the stash entry to be upgraded to a typeglob
+(i.e. this is just an internal implementation detail).
+This optimization does not currently apply to XSUBs or exported
+subroutines, and method calls will undo it, since they cache things in
+typeglobs.
L<[perl #120441]|https://rt.perl.org/Ticket/Display.html?id=120441>
=item *
=item *
Win32 Perl uses 8 KB less of per-process memory than before for every perl
-process of this version. This data is now memory mapped from disk and shared
-between perl processes from the same perl binary.
+process, because some data is now memory mapped from disk and shared
+between processes from the same perl binary.
=back
=head1 Modules and Pragmata
-XXX All changes to installed files in F<cpan/>, F<dist/>, F<ext/> and F<lib/>
-go here. If Module::CoreList is updated, generate an initial draft of the
-following sections using F<Porting/corelist-perldelta.pl>. A paragraph summary
-for important changes should then be added by hand. In an ideal world,
-dual-life modules would have a F<Changes> file that could be cribbed.
+Many of the libraries distributed with perl have been upgraded since v5.20.0.
+For a complete list of changes, run:
-[ Within each section, list entries as a =item entry ]
+ corelist --diff 5.20.0 5.22.0
-=head2 New Modules and Pragmata
-
-=over 4
-
-=item *
+You can substitute your favorite version in place of 5.20.0, too.
-XXX
-
-=back
+=head2 Removed Modules and Pragmata
-=head2 Updated Modules and Pragmata
+The following modules (and associated modules) have been removed from the core
+perl distribution:
=over 4
=item *
-L<XXX> has been upgraded from version A.xx to B.yy.
-
-=back
-
-=head2 Removed Modules and Pragmata
-
-=over 4
+L<CGI>
=item *
-XXX
+L<Module::Build>
=back
=item *
-C<sv_usepvn_flags> - Fix documentation to mention the use of C<NewX> instead of
+C<sv_usepvn_flags> - fix documentation to mention the use of C<Newx> instead of
C<malloc>.
L<[perl #121869]|https://rt.perl.org/Ticket/Display.html?id=121869>
=item *
-Previously missing documentation due to formatting errors are now included.
+Some documentation that was previously missing due to formatting errors is
+now included.
=item *
=item *
Note that C<exec LIST> and C<system LIST> may fall back to the shell on
-Win32. Only C<exec PROGRAM LIST> and C<system PROGRAM LIST> indirect object
-syntax will reliably avoid using the shell.
+Win32. Only the indirect-object syntax C<exec PROGRAM LIST> and
+C<system PROGRAM LIST> will reliably avoid using the shell.
This has also been noted in L<perlport>.
=item *
-Documentation has been added illustrating the perils of assuming the contents
-of static memory pointed to by the return values of Perl wrappers for C library
-functions doesn't change.
+Documentation has been added illustrating the perils of assuming that
+there is no change to the contents of static memory pointed to by the
+return values of Perl's wrappers for C library functions.
=item *
-Recommended replacements for tmpfile, atoi, strtol, and strtoul added.
+Replacements for C<tmpfile>, C<atoi>, C<strtol>, and C<strtoul> are now
+recommended.
=item *
=item *
-Out-of-date VMS-specific information has been fixed/simplified.
+Out-of-date VMS-specific information has been fixed and/or simplified.
=item *
=item *
-The C</x> modifier has been clarified to note that comments cannot be continued
-onto the next line by escaping them.
+The description of the C</x> modifier has been clarified to note that
+comments cannot be continued onto the next line by escaping them.
=back
L<:const is not permitted on named subroutines|perldiag/":const is not permitted on named subroutines">
(F) The "const" attribute causes an anonymous subroutine to be run and
-its value captured at the time that it is cloned. Names subroutines are
+its value captured at the time that it is cloned. Named subroutines are
not cloned like this, so the attribute does not make sense on them.
=item *
=item *
+L<\C is deprecated in regex|perldiag/"\C is deprecated in regex; marked by <-- HERE in m/%s/">
+
+(D deprecated) The C<< /\C/ >> character class was deprecated in v5.20, and
+now emits a warning. It is intended that it will become an error in v5.24.
+This character class matches a single byte even if it appears within a
+multi-byte character, breaks encapsulation, and can corrupt UTF-8
+strings.
+
+=item *
+
L<'%s' is an unknown bound type in regex|perldiag/"'%s' is an unknown bound type in regex; marked by <-- HERE in m/%s/">
You used C<\b{...}> or C<\B{...}> and the C<...> is not known to
L<Redundant argument in %s|perldiag/Redundant argument in %s>
-(W redundant) You called a function with more arguments than other
-arguments you supplied indicated would be needed. Currently only
-emitted when a printf-type format required fewer arguments than were
-supplied, but might be used in the future for e.g. L<perlfunc/pack>.
+(W redundant) You called a function with more arguments than were
+needed, as indicated by information within other arguments you supplied
+(e.g. a printf format). Currently only emitted when a printf-type format
+required fewer arguments than were supplied, but might be used in the
+future for e.g. L<perlfunc/pack>.
The warnings category C<< redundant >> is new. See also
L<[perl #121025]|https://rt.perl.org/Ticket/Display.html?id=121025>.
L<Use of literal non-graphic characters in variable names is deprecated|perldiag/"Use of literal non-graphic characters in variable names is deprecated">
+(D deprecated) Using literal non-graphic (including control)
+characters in the source to refer to the ^FOO variables, like C<$^X> and
+C<${^GLOBAL_PHASE}> is now deprecated.
+
=item *
L<Useless use of attribute "const"|perldiag/Useless use of attribute "const">
=item *
+L<Warning: unable to close filehandle properly: %s|perldiag/"Warning: unable to close filehandle properly: %s">
+
L<Warning: unable to close filehandle %s properly: %s|perldiag/"Warning: unable to close filehandle %s properly: %s">
+(S io) Previously perl silently ignored any errors when doing an implicit
+close of a filehandle, i.e. where the reference count of the filehandle
+reached zero and the user's code hadn't already called C<close()>; e.g.
+
+ {
+ open my $fh, '>', $file or die "open: '$file': $!\n";
+ print $fh, $data or die;
+ } # implicit close here
+
+In a situation such as disk full, due to buffering the error may only be
+detected during the final close, so not checking the result of the close is
+dangerous.
+
+So perl now warns in such situations.
+
=item *
L<Wide character (U+%X) in %s|perldiag/"Wide character (U+%X) in %s">
(W locale) While in a single-byte locale (I<i.e.>, a non-UTF-8
one), a multi-byte character was encountered. Perl considers this
-character to be the specified Unicode code point. Combining non-UTF8
+character to be the specified Unicode code point. Combining non-UTF-8
locales and Unicode is dangerous. Almost certainly some characters
will have two different representations. For example, in the ISO 8859-7
(Greek) locale, the code point 0xC3 represents a Capital Gamma. But so
L<Locale '%s' may not work well.%s|perldiag/Locale '%s' may not work well.%s>
+(W locale) You are using the named locale, which is a non-UTF-8 one, and
+which Perl has determined is not fully compatible with Perl. The second
+C<%s> gives a reason.
+
=item *
L<Can't do %s("%s") on non-UTF-8 locale; resolved to "%s".|perldiag/Can't do %s("%s") on non-UTF-8 locale; resolved to "%s".>
+(W locale) You are 1) running under "C<use locale>"; 2) the current
+locale is not a UTF-8 one; 3) you tried to do the designated case-change
+operation on the specified Unicode character; and 4) the result of this
+operation would mix Unicode and locale rules, which likely conflict.
+
=back
+=item *
+
+L<Missing or undefined argument to require|perldiag/Missing or undefined argument to require>
+
+(F) You tried to call require with no argument or with an undefined
+value as an argument. Require expects either a package name or a
+file-specification as an argument. See L<perlfunc/require>.
+
+Formerly, C<require> with no argument or undef warned about a Null filename.
+
=back
=head2 Changes to Existing Diagnostics
=item *
L<Argument "%s" isn't numeric%s|perldiag/"Argument "%s" isn't numeric%s">
-now adds the following note:
+
+The L<perldiag> entry for this warning has added this clarifying note:
Note that for the Inf and NaN (infinity and not-a-number) the
definition of "numeric" is somewhat unusual: the strings themselves
=item *
-L<\N{} in character class restricted to one character in regex; marked by S<<-- HERE> in mE<sol>%sE<sol>|perldiag/"\N{} in inverted character class or as a range end-point is restricted to one character in regex; marked by <-- HERE in m/%s/">
+L<<< \N{} in character class restricted to one character in regex; marked by
+S<< <-- HERE >> in mE<sol>%sE<sol>|perldiag/"\N{} in inverted character
+class or as a range end-point is restricted to one character in regex;
+marked by <-- HERE in m/%s/" >>>
-This message has had 'character class' changed to 'inverted character class or
-as a range end-point is' to reflect improvements in C<qr/[\N{named sequence}]/>
-(see under L</Selected Bug Fixes>).
+This message has had I<character class> changed to I<inverted character
+class or as a range end-point is> to reflect improvements in
+C<qr/[\N{named sequence}]/> (see under L</Selected Bug Fixes>).
=item *
L<panic: frexp|perldiag/"panic: frexp: %f">
-This message has had ': C<%f>' appended to it, to show what the offending floating
-point number is.
+This message has had ': C<%f>' appended to it, to show what the offending
+floating point number is.
=item *
-
B<Possible precedence problem on bitwise %c operator> reworded as
+
I<Possible precedence problem on bitwise %c operator> reworded as
L<Possible precedence problem on bitwise %s operator|perldiag/"Possible precedence problem on bitwise %s operator">.
=item *
-C<require> with no argument or undef used to warn about a Null filename; now
-it dies with C<Missing or undefined argument to require>.
-
-=item *
-
L<Unsuccessful %s on filename containing newline|perldiag/"Unsuccessful %s on filename containing newline">
This warning is now only produced when the newline is at the end of
L<Variable length lookbehind not implemented in regex mE<sol>%sE<sol>|perldiag/"Variable length lookbehind not implemented in regex m/%s/">
-Information about Unicode behaviour has been added.
+The L<perldiag> entry for this warning has had information about Unicode
+behaviour added.
=back
=head1 Utility Changes
-=head2 F<x2p/>
+=head2 F<find2perl>, F<s2p> and F<a2p> removal
=over 4
=item *
-No longer depends on non-core module anymore.
+No longer depends on non-core modules.
=back
=item *
-F<Configure> now checks for F<lrintl>, F<lroundl>, F<llrintl>, and F<llroundl>.
+F<Configure> now checks for C<lrintl()>, C<lroundl()>, C<llrintl()>, and
+C<llroundl()>.
=item *
=item *
-pthreads and lcl will be linked by default if present. This allows XS modules
-that require threading to work on non-threaded perls. Note that you must still
-pass C<-Dusethreads> if you want a threaded perl.
+The C<pthreads> and C<cl> libraries will be linked by default if present.
+This allows XS modules that require threading to work on non-threaded
+perls. Note that you must still pass C<-Dusethreads> if you want a
+threaded perl.
=item *
For long doubles (to get more precision and range for floating point numbers)
one can now use the GCC quadmath library which implements the quadruple
-precision floating point numbers in x86 and ia64 platforms. See F<INSTALL> for
-details.
+precision floating point numbers on x86 and IA-64 platforms. See
+F<INSTALL> for details.
=item *
A new compilation flag, C<< -DPERL_OP_PARENT >> is available. For details,
see the discussion below at L<< /Internal Changes >>.
+=item *
+
+Pathtools no longer tries to load XS on miniperl. This speeds up building perl
+slightly.
+
=back
=head1 Testing
F<t/porting/re_context.t> has been added to test that L<utf8> and its
dependencies only use the subset of the C<$1..$n> capture vars that
-C<Perl_save_re_context()> is hard-coded to localize, because that function has no
-efficient way of determining at runtime what vars to localize.
+C<Perl_save_re_context()> is hard-coded to localize, because that function
+has no efficient way of determining at runtime what vars to localize.
=item *
=item NeXTSTEP/OPENSTEP
-NeXTSTEP was proprietary OS bundled with NeXT's workstations in the early
-to mid 90s; OPENSTEP was an API specification that provided a NeXTSTEP-like
-environment on a non-NeXTSTEP system. Both are now long dead, so support
-for building Perl on them has been removed.
+NeXTSTEP was a proprietary operating system bundled with NeXT's
+workstations in the early to mid 90s; OPENSTEP was an API specification
+that provided a NeXTSTEP-like environment on a non-NeXTSTEP system. Both
+are now long dead, so support for building Perl on them has been removed.
=back
=item *
-C<test-prep> again depends on C<test-prep-gcc> for GCC builds.
-L<[perl #124221]|https://rt.perl.org/Ticket/Display.html?id=124221>
+C<nmake minitest> now works on Win32. Due to dependency issues you
+need to build C<nmake test-prep> first, and a small number of the
+tests fail.
+L<[perl #123394]|https://rt.perl.org/Ticket/Display.html?id=123394>
=item *
=item *
-List form pipe open no longer falls back to the shell.
-
-=item *
-
-XXX In release 5.21.8 compiling on VC with dmake was broken. Fixed.
+The list form of piped open has been implemented for Win32. Note: unlike
+C<system LIST> this does not fall back to the shell.
+L<[perl #121159]|https://rt.perl.org/Ticket/Display.html?id=121159>
=item *
=item *
-L<B> now compiles again on Windows.
-
-=item *
-
-Previously, on Visual C++ for Win64 built Perls only, when compiling every Perl
-XS module (including CPAN ones) and Perl aware .c file with a 64 bit Visual C++,
-would unconditionally have around a dozen warnings from hv_func.h. These
-warnings have been silenced. GCC all bitness and Visual C++ for Win32 were
-not affected.
+Previously compiling XS modules (including CPAN ones) using Visual C++ for
+Win64 resulted in around a dozen warnings per file from F<hv_func.h>. These
+warnings have been silenced.
=item *
=item *
-Between 2 and 6 ms and 7 I/O calls have been saved per attempt to open a perl
-module for each path in C<@INC>.
+Between 2 and 6 milliseconds and seven I/O calls have been saved per attempt
+to open a perl module for each path in C<@INC>.
=item *
=item *
In the experimental C<:win32> layer, a crash in C<open> was fixed. Also
-opening C</dev/null>, which works the Win32 Perl's normal C<:unix> layer, was
-implemented for C<:win32>.
+opening C</dev/null> (which works under Win32 Perl's default C<:unix>
+layer) was implemented for C<:win32>.
L<[perl #122224]|https://rt.perl.org/Ticket/Display.html?id=122224>
=item *
=item *
-C<c99> options have been cleaned up, hints look for C<solstudio>
-as well as C<SUNWspro>, and support for native C<setenv> has been added.
+C<c99> options have been cleaned up; hints look for C<solstudio>
+as well as C<SUNWspro>; and support for native C<setenv> has been added.
=back
Experimental support has been added to allow ops in the optree to locate
their parent, if any. This is enabled by the non-default build option
C<-DPERL_OP_PARENT>. It is envisaged that this will eventually become
-enabled by default, so XS code which directly accesses the C<op_silbing>
+enabled by default, so XS code which directly accesses the C<op_sibling>
field of ops should be updated to be future-proofed.
On C<PERL_OP_PARENT> builds, the C<op_sibling> field has been renamed
C<op_sibparent> and a new flag, C<op_moresib>, added. On the last op in a
sibling chain, C<op_moresib> is false and C<op_sibparent> points to the
-parent (if any) rather than to being C<NULL>.
+parent (if any) rather than being C<NULL>.
-To make existing code work transparently whether using C<-DPERL_OP_PARENT>
+To make existing code work transparently whether using C<PERL_OP_PARENT>
or not, a number of new macros and functions have been added that should
be used, rather than directly manipulating C<op_sibling>.
two new macros have been added. A simple scan through a sibling chain
like this:
- for (; kid->op_sibling; kid = kid->op_sibling) { ... }
+ for (; kid->op_sibling; kid = kid->op_sibling) { ... }
should now be written as:
- for (; OpHAS_SIBLING(kid); kid = OpSIBLING(kid)) { ... }
+ for (; OpHAS_SIBLING(kid); kid = OpSIBLING(kid)) { ... }
-For altering optrees, A general-purpose function C<op_sibling_splice()>
+For altering optrees, a general-purpose function C<op_sibling_splice()>
has been added, which allows for manipulation of a chain of sibling ops.
By analogy with the Perl function C<splice()>, it allows you to cut out
zero or more ops from a sibling chain and replace them with zero or more
parent at the same time (e.g. by updating C<op_first> and C<op_last> where
appropriate).
-A C-level C<Perl_op_parent()> function and a perl-level C<B::OP::parent()>
+A C-level C<Perl_op_parent()> function and a Perl-level C<B::OP::parent()>
method have been added. The C function only exists under
-C<-DPERL_OP_PARENT> builds (using it is build-time error on vanilla
+C<PERL_OP_PARENT> builds (using it is build-time error on vanilla
perls). C<B::OP::parent()> exists always, but on a vanilla build it
-always returns C<NULL>. Under C<-DPERL_OP_PARENT>, they return the parent
+always returns C<NULL>. Under C<PERL_OP_PARENT>, they return the parent
of the current op, if any. The variable C<$B::OP::does_parent> allows you
to determine whether C<B> supports retrieving an op's parent.
-XXX C<-DPERL_OP_PARENT> was introduced in 5.21.2, but the interface was
+C<PERL_OP_PARENT> was introduced in 5.21.2, but the interface was
changed considerably in 5.21.11. If you updated your code before the
5.21.11 changes, it may require further revision. The main changes after
5.21.2 were:
=item *
-Added C<Perl_sv_get_backrefs()> to determine if an SV is a weak-referent.
-
-Function either returns an SV * of type AV, which contains the set of
-weakreferences which reference the passed in SV, or a simple RV * which
-is the only weakref to this item.
+A new function, C<Perl_sv_get_backrefs()>, has been added which allows you
+retrieve the weak references, if any, which point at an SV.
=item *
-C<screaminstr> has been removed. Although marked as public API, it is
-undocumented and has no usage in modern perl versions on CPAN Grep. Calling it
-has been fatal since 5.17.0.
+The C<screaminstr()> function has been removed. Although marked as
+public API, it was undocumented and had no usage in CPAN modules. Calling
+it has been fatal since 5.17.0.
=item *
-C<newDEFSVOP>, C<block_start>, C<block_end> and C<intro_my> have been added
-to the API.
+The C<newDEFSVOP()>, C<block_start()>, C<block_end()> and C<intro_my()>
+functions have been added to the API.
=item *
=item *
-C<sv_magic> no longer forbids "ext" magic on read-only values. After all,
-perl can't know whether the custom magic will modify the SV or not.
+The C<sv_magic()> function no longer forbids "ext" magic on read-only
+values. After all, perl can't know whether the custom magic will modify
+the SV or not.
L<[perl #123103]|https://rt.perl.org/Ticket/Display.html?id=123103>.
=item *
-Accessing L<perlapi/CvPADLIST> in an XSUB is now forbidden.
-C<CvPADLIST> has been reused for a different internal purpose for XSUBs. Guard all
-C<CvPADLIST> expressions with C<CvISXSUB()> if your code doesn't already block
-XSUB CV*s from going through optree CV* expecting code.
+Accessing L<perlapi/CvPADLIST> on an XSUB is now forbidden.
+
+The C<CvPADLIST> field has been reused for a different internal purpose
+for XSUBs. So in particular, you can no longer rely on it being NULL as a
+test of whether a CV is an XSUB. Use C<CvISXSUB()> instead.
=item *
-SVs of type SVt_NV are now bodyless when a build configure and platform allow
-it, specifically C<sizeof(NV) <= sizeof(IV)>. The bodyless trick is the same one
-as for IVs since 5.9.2, but for NVs, unlike IVs, is not guaranteed on all
-platforms and build configurations.
+SVs of type C<SVt_NV> are now sometimes bodiless when the build
+configuration and platform allow it: specifically, when C<< sizeof(NV) <=
+sizeof(IV) >>. "Bodiless" means that the NV value is stored directly in
+the head of an SV, without requiring a separate body to be allocated. This
+trick has already been used for IVs since 5.9.2 (though in the case of
+IVs, it is always used, regardless of platform and build configuration).
=item *
-The C<$DB::single>, C<$DB::signal> and C<$DB::trace> now have set and
-get magic that stores their values as IVs and those IVs are used when
-testing their values in C<pp_dbstate>. This prevents perl from
-recursing infinity if an overloaded object is assigned to any of those
+The C<$DB::single>, C<$DB::signal> and C<$DB::trace> variables now have set- and
+get-magic that stores their values as IVs, and those IVs are used when
+testing their values in C<pp_dbstate()>. This prevents perl from
+recursing infinitely if an overloaded object is assigned to any of those
variables.
L<[perl #122445]|https://rt.perl.org/Ticket/Display.html?id=122445>.
=item *
-C<Perl_tmps_grow> which is marked as public API but undocumented has been
-removed from public API. If you use C<EXTEND_MORTAL> macro in your XS code to
-preextend the mortal stack, you are unaffected by this change.
-
-=item *
-
-XXX C<cv_name>, which was introduced in 5.21.4, has been changed incompatibly.
-It now has a flags field that allows the caller to specify whether the name
-should be fully qualified. See L<perlapi/cv_name>.
+C<Perl_tmps_grow()>, which is marked as public API but is undocumented, has
+been removed from the public API. This change does not affect XS code that
+uses the C<EXTEND_MORTAL> macro to pre-extend the mortal stack.
=item *
-Internally Perl no longer uses the C<SVs_PADMY> flag. C<SvPADMY()> now
-returns a true value for anything not marked PADTMP. C<SVs_PADMY> is now
-defined as 0.
+Perl's internals no longer sets or uses the C<SVs_PADMY> flag.
+C<SvPADMY()> now returns a true value for anything not marked C<PADTMP>
+and C<SVs_PADMY> is now defined as 0.
=item *
-The macros SETsv and SETsvUN have been removed. They were no longer used
-in the core since commit 6f1401dc2a, and have not been found present on
-CPAN.
+The macros C<SETsv> and C<SETsvUN> have been removed. They were no longer used
+in the core since commit 6f1401dc2a five years ago, and have not been
+found present on CPAN.
=item *
=item *
-The C<sv_catpvn_flags> function accepts C<SV_CATBYTES> and C<SV_CATUTF8>
-flags, which specify whether the appended string is bytes or utf8,
-respectively.
+The C<sv_catpvn_flags()> function accepts C<SV_CATBYTES> and C<SV_CATUTF8>
+flags, which specify whether the appended string is bytes or UTF-8,
+respectively. (These flags have in fact been present since 5.16.0, but
+were formerly not regarded as part of the API.)
=item *
-A new opcode class, C<< METHOP >> has been introduced, which holds
-class/method related info needed at runtime to improve performance
+A new opcode class, C<< METHOP >>, has been introduced. It holds
+information used at runtime for improve the performance
of class/object method calls.
-C<< OP_METHOD >> and C<< OP_METHOD_NAMED >> are moved from being
+C<< OP_METHOD >> and C<< OP_METHOD_NAMED >> have changed from being
C<< UNOP/SVOP >> to being C<< METHOP >>.
=item *
-C<save_re_context> no longer does anything and has been moved to F<mathoms.c>.
+C<cv_name()> is a new API function that can be passed a CV or GV. It
+returns an SV containing the name of the subroutine, for use in
+diagnostics.
-=item *
+Note that after C<cv_name> was introduced in 5.21.4, it had a C<flags>
+field added in 5.21.5 which allows the caller to specify whether the name
+should be fully qualified. See L<perlapi/cv_name>.
-C<cv_name> is a new API function that can be passed a CV or GV. It returns an
-SV containing the name of the subroutine for use in diagnostics.
L<[perl #116735]|https://rt.perl.org/Ticket/Display.html?id=116735>
L<[perl #120441]|https://rt.perl.org/Ticket/Display.html?id=120441>
=item *
-C<cv_set_call_checker_flags> is a new API function that works like
-C<cv_set_call_checker>, except that it allows the caller to specify whether the
-call checker requires a full GV for reporting the subroutine's name, or whether
-it could be passed a CV instead. Whatever value is passed will be acceptable
-to C<cv_name>. C<cv_set_call_checker> guarantees there will be a GV, but it
-may have to create one on the fly, which is inefficient.
+C<cv_set_call_checker_flags()> is a new API function that works like
+C<cv_set_call_checker()>, except that it allows the caller to specify
+whether the call checker requires a full GV for reporting the subroutine's
+name, or whether it could be passed a CV instead. Whatever value is
+passed will be acceptable to C<cv_name()>. C<cv_set_call_checker()>
+guarantees there will be a GV, but it may have to create one on the fly,
+which is inefficient.
L<[perl #116735]|https://rt.perl.org/Ticket/Display.html?id=116735>
=item *
C<CvGV> (which is not part of the API) is now a more complex macro, which may
-call a function and reify a GV. For those cases where is has been used as a
+call a function and reify a GV. For those cases where it has been used as a
boolean, C<CvHASGV> has been added, which will return true for CVs that
notionally have GVs, but without reifying the GV. C<CvGV> also returns a GV
now for lexical subs.
=item *
-Added L<perlapi/sync_locale>. Changing the program's locale should be avoided
-by XS code. Nevertheless, certain non-Perl libraries called from XS, such as
-C<Gtk> do so. When this happens, Perl needs to be told that the locale has
+The L<perlapi/sync_locale> function has been added to the public API.
+Changing the program's locale should be avoided by XS code. Nevertheless,
+certain non-Perl libraries called from XS need to do so, such as C<Gtk>.
+When this happens, Perl needs to be told that the locale has
changed. Use this function to do so, before returning to Perl.
=item *
auto-generated from data in F<regen/op_private>. The noticeable effect of this
is that some of the flag output of C<Concise> might differ slightly, and the
flag output of C<perl -Dx> may differ considerably (they both use the same set
-of labels now). Also in debugging builds, there is a new assert in
-C<op_free()> that checks that the op doesn't have any unrecognized flags set in
+of labels now). Also, debugging builds now have a new assertion in
+C<op_free()> to ensure that the op doesn't have any unrecognized flags set in
C<op_private>.
=item *
=item *
-The following private API functions had their context parameter removed,
+The following private API functions had their context parameter removed:
C<Perl_cast_ulong>, C<Perl_cast_i32>, C<Perl_cast_iv>, C<Perl_cast_uv>,
C<Perl_cv_const_sv>, C<Perl_mg_find>, C<Perl_mg_findext>, C<Perl_mg_magical>,
C<Perl_mini_mktime>, C<Perl_my_dirfd>, C<Perl_sv_backoff>, C<Perl_utf8_hop>.
-Users of the public API prefix-less calls remain unaffected.
+Note that the prefix-less versions of those functions that are part of the
+public API, such as C<cast_i32()>, remain unaffected.
=item *
-The PADNAME and PADNAMELIST types are now separate types, and no longer
-simply aliases for SV and AV.
+The C<PADNAME> and C<PADNAMELIST> types are now separate types, and no
+longer simply aliases for SV and AV.
L<[perl #123223]|https://rt.perl.org/Ticket/Display.html?id=123223>.
=item *
-Pad names are now always UTF8. The C<PadnameUTF8> macro always returns
+Pad names are now always UTF
-8. The C<PadnameUTF8> macro always returns
true. Previously, this was effectively the case already, but any support
for two different internal representations of pad names has now been
removed.
=item *
-C<pack("D", $x)> and C<pack("F", $x)> now zero the padding on x86 long double
-builds. GCC 4.8 and later, under some build options, would either overwrite
-the zero-initialized padding, or bypass the initialized buffer entirely. This
-caused F<op/pack.t> to fail.
+C<pack("D", $x)> and C<pack("F", $x)> now zero the padding on x86 long
+double builds. Under some build options on GCC 4.8 and later, they used
+to either overwrite the zero-initialized padding, or bypass the
+initialized buffer entirely. This caused F<op/pack.t> to fail.
L<[perl #123971]|https://rt.perl.org/Ticket/Display.html?id=123971>
=item *
=item *
-XXX An optimization for state variable initialization introduced in Perl 5.21.6 has
-been reverted because it was found to exacerbate some other existing buggy
-behaviour.
-L<[perl #124160]|https://rt.perl.org/Ticket/Display.html?id=124160>
-
-=item *
-
-XXX The extension of another optimization to cover more ops in Perl 5.21 has also
-been reverted to its Perl 5.20 state as a temporary fix for regression issues
-that it caused.
-L<[perl #123790]|https://rt.perl.org/Ticket/Display.html?id=123790>
-
-=item *
-
-A possible crashing/looping bug has been fixed.
+A possible crashing/looping bug related to compiling lexical subs has been
+fixed.
L<[perl #124099]|https://rt.perl.org/Ticket/Display.html?id=124099>
=item *
-UTF-8 variable names used in array indexes, unquoted UTF-8 HERE-document
-terminators and UTF-8 function names all now work correctly.
+UTF-8 now works correctly in function names, in unquoted HERE-document
+terminators, and in variable names used as array indexes.
L<[perl #124113]|https://rt.perl.org/Ticket/Display.html?id=124113>
=item *
=item *
-C<split> in the scope of lexical C<$>_ has been fixed not to fail assertions.
+C<split> in the scope of lexical C<$_> has been fixed not to fail assertions.
L<[perl #123763]|https://rt.perl.org/Ticket/Display.html?id=123763>
=item *
=item *
An C<@> sign in quotes followed by a non-ASCII digit (which is not a valid
-identifier) would cause the parser to crash, instead of simply trying the C<@> as
-literal. This has been fixed.
+identifier) would cause the parser to crash, instead of simply trying the
+C<@> as literal. This has been fixed.
L<[perl #123963]|https://rt.perl.org/Ticket/Display.html?id=123963>
=item *
=item *
C<foreach> in scalar context was not pushing an item on to the stack, resulting
-in bugs. (S<C<print 4, scalar do { foreach(@x){} } + 1>> would print 5.) It has
-been fixed to return C<undef>.
+in bugs. (S<C<print 4, scalar do { foreach(@x){} } + 1>> would print 5.)
+It has been fixed to return C<undef>.
L<[perl #124004]|https://rt.perl.org/Ticket/Display.html?id=124004>
=item *
-A regression in the behaviour of the C<readline> built-in function, caused by
-the introduction of the C<< <<>> >> operator, has been fixed.
-L<[perl #123990]|https://rt.perl.org/Ticket/Display.html?id=123990>
-
-=item *
-
Several cases of data used to store environment variable contents in core C
code being potentially overwritten before being used have been fixed.
L<[perl #123748]|https://rt.perl.org/Ticket/Display.html?id=123748>
=item *
-Patterns starting with C</.*/> are now fast again.
+Some patterns starting with C</.*..../> matched against long strings have
+been slow since v5.8, and some of the form C</.*..../i> have been slow
+since v5.18. They are now all fast again.
L<[perl #123743]|https://rt.perl.org/Ticket/Display.html?id=123743>.
=item *
=item *
-Fix a couple of size calculation overflows.
-L<[perl #123554]|https://rt.perl.org/Ticket/Display.html?id=123554>.
-
-=item *
-
Perl 5.14.0 introduced a bug whereby C<eval { LABEL: }> would crash. This
has been fixed.
L<[perl #123652]|https://rt.perl.org/Ticket/Display.html?id=123652>.
=item *
-Only stringy classnames are now shared. This fixes some failures in L<autobox>.
-L<[perl #100819]|https://rt.cpan.org/Ticket/Display.html?id=100819>.
-
-=item *
-
A bug in regular expression patterns that could lead to segfaults and
other crashes has been fixed. This occurred only in patterns compiled
-with C<"/i">, while taking into account the current POSIX locale (this usually
-means they have to be compiled within the scope of C<S<"use locale">>),
+with C</i> while taking into account the current POSIX locale (which usually
+means they have to be compiled within the scope of C<S<use locale>>),
and there must be a string of at least 128 consecutive bytes to match.
L<[perl #123539]|https://rt.perl.org/Ticket/Display.html?id=123539>.
=item *
-C<s///> now works on very long strings instead of dying with 'Substitution
-loop'.
+C<s///g> now works on very long strings (where there are more than 2
+billion iterations) instead of dying with 'Substitution loop'.
L<[perl #103260]|https://rt.perl.org/Ticket/Display.html?id=103260>.
L<[perl #123071]|https://rt.perl.org/Ticket/Display.html?id=123071>.
=item *
-C<\()> (reference to an empty list) and C<y///> with lexical C<$_> in scope
-could do a bad write past the end of the stack. They have been fixed
-to extend the stack first.
+C<\()> (a reference to an empty list), and C<y///> with lexical C<$_> in
+scope, could both do a bad write past the end of the stack. They have
+both been fixed to extend the stack first.
=item *
=item *
-Some cases of lexical state subs inside predeclared subs could crash but no
-longer do.
+Some cases of lexical state subs declared inside predeclared subs could
+crash, for example when evalling a string including the name of an outer
+variable, but no longer do.
=item *
Some cases of nested lexical state subs inside anonymous subs could cause
-'Bizarre copy' errors or possibly even crash.
+'Bizarre copy' errors or possibly even crashes.
=item *
=item *
-Certain syntax errors in substitutions, such as C<< s/${E<lt>E<gt>{})// >>, would
+Certain syntax errors in substitutions, such as C<< s/${<>{})// >>, would
crash, and had done so since Perl 5.10. (In some cases the crash did not
start happening till 5.16.) The crash has, of course, been fixed.
L<[perl #123542]|https://rt.perl.org/Ticket/Display.html?id=123542>.
=item *
-A repeat expression like C<33 x ~3> could cause a large buffer
+Fix a couple of string grow size calculation overflows; in particular,
+a repeat expression like C<33 x ~3> could cause a large buffer
overflow since the new output buffer size was not correctly handled by
SvGROW(). An expression like this now properly produces a memory wrap
panic.
=item *
-op_free() no longer crashes due to a stack overflow when freeing a
-deeply recursive op tree.
-L<[perl #108276]|https://rt.perl.org/Ticket/Display.html?id=108276>.
-
-=item *
-
-scalarvoid() would crash due to a stack overflow when processing a
-deeply recursive op tree.
+C<op_free()> and C<scalarvoid()> no longer crash due to a stack overflow
+when freeing a deeply recursive op tree.
L<[perl #108276]|https://rt.perl.org/Ticket/Display.html?id=108276>.
=item *
-In Perl 5.20.0, C<$^N> accidentally had the internal UTF8 flag turned off
+In Perl 5.20.0, C<$^N> accidentally had the internal UTF-8 flag turned off
if accessed from a code block within a regular expression, effectively
-UTF8-encoding the value. This has been fixed.
+UTF-8-encoding the value. This has been fixed.
L<[perl #123135]|https://rt.perl.org/Ticket/Display.html?id=123135>.
=item *
A failed C<semctl> call no longer overwrites existing items on the stack,
-causing C<(semctl(-1,0,0,0))[0]> to give an "uninitialized" warning.
+which means that C<(semctl(-1,0,0,0))[0]> no longer gives an
+"uninitialized" warning.
=item *
=item *
-Sometimes the assignment in C<@array = split> gets optimised and C<split>
+Sometimes the assignment in C<@array = split> gets optimised so that C<split>
itself writes directly to the array. This caused a bug, preventing this
assignment from being used in lvalue context. So
C<(@a=split//,"foo")=bar()> was an error. (This bug probably goes back to
-Perl 3, when the optimisation was added.) This optimisation, and the bug,
-started to happen in more cases in XXX 5.21.5. It has now been fixed.
+Perl 3, when the optimisation was added.) It has now been fixed.
L<[perl #123057]|https://rt.perl.org/Ticket/Display.html?id=123057>.
=item *
-When argument lists that fail the checks installed by subroutine
-signatures, the resulting error messages now give the file and line number
-of the caller, not of the called subroutine.
+When an argument list fails the checks specified by a subroutine
+signature (which is still an experimental feature), the resulting error
+messages now give the file and line number of the caller, not of the
+called subroutine.
L<[perl #121374]|https://rt.perl.org/Ticket/Display.html?id=121374>.
=item *
-Flip-flop operators (C<..> and C<...> in scalar context) used to maintain
+The flip-flop operators (C<..> and C<...> in scalar context) used to maintain
a separate state for each recursion level (the number of times the
enclosing sub was called recursively), contrary to the documentation. Now
each closure has one internal state for each flip-flop.
=item *
+The flip-flop operator (C<..> in scalar context) would return the same
+scalar each time, unless the containing subroutine was called recursively.
+Now it always returns a new scalar.
+L<[perl #122829]|https://rt.perl.org/Ticket/Display.html?id=122829>.
+
+=item *
+
C<use>, C<no>, statement labels, special blocks (C<BEGIN>) and pod are now
permitted as the first thing in a C<map> or C<grep> block, the block after
C<print> or C<say> (or other functions) returning a handle, and within
=item *
C<(...) x ...> in scalar context used to corrupt the stack if one operand
-were an object with "x" overloading, causing erratic behaviour.
+was an object with "x" overloading, causing erratic behaviour.
L<[perl #121827]|https://rt.perl.org/Ticket/Display.html?id=121827>.
=item *
-Assignment to a lexical scalar is often optimised away (as mentioned under
-L</Performance Enhancements>). Various bugs related to this optimisation
-have been fixed. Certain operators on the right-hand side would sometimes
-fail to assign the value at all or assign the wrong value, or would call
-STORE twice or not at all on tied variables. The operators affected were
-C<$foo++>, C<$foo-->, and C<-$foo> under C<use integer>, C<chomp>, C<chr>
-and C<setpgrp>.
+Assignment to a lexical scalar is often optimised away; for example in
+C<my $x; $x = $y + $z>, the assign operator is optimised away and the add
+operator writes its result directly to C<$x>. Various bugs related to
+this optimisation have been fixed. Certain operators on the right-hand
+side would sometimes fail to assign the value at all or assign the wrong
+value, or would call STORE twice or not at all on tied variables. The
+operators affected were C<$foo++>, C<$foo-->, and C<-$foo> under C<use
+integer>, C<chomp>, C<chr> and C<setpgrp>.
=item *
List assignments were sometimes buggy if the same scalar ended up on both
-sides of the assignment due to used of C<tied>, C<values> or C<each>. The
+sides of the assignment due to use of C<tied>, C<values> or C<each>. The
result would be the wrong value getting assigned.
=item *
=item *
Inlining of subs with an empty prototype is now more consistent than
-before. Previously, a sub with multiple statements, all but the last
-optimised away, would be inlinable only if it were an anonymous sub
+before. Previously, a sub with multiple statements, of which all but the last
+were optimised away, would be inlinable only if it were an anonymous sub
containing a string C<eval> or C<state> declaration or closing over an
outer lexical variable (or any anonymous sub under the debugger). Now any
sub that gets folded to a single constant after statements have been
=item *
On some systems, such as VMS, C<crypt> can return a non-ASCII string. If a
-scalar assigned to had contained a UTF8 string previously, then C<crypt>
-would not turn off the UTF8 flag, thus corrupting the return value. This
+scalar assigned to had contained a UTF-8 string previously, then C<crypt>
+would not turn off the UTF-8 flag, thus corrupting the return value. This
would happen with C<$lexical = crypt ...>.
=item *
=item *
-Fixed two assertion failures introduced into C<-DPERL_OP_PARENT>
-builds.
-L<[perl #108276]|https://rt.perl.org/Ticket/Display.html?id=108276>.
-
-=item *
-
C<index()> and C<rindex()> no longer crash when used on strings over 2GB in
size.
L<[perl #121562]|https://rt.perl.org/Ticket/Display.html?id=121562>.
C<[[:word:]]>,
and
C<[[:xdigit:]]>.
-These are because the underlying Microsoft implementation does not
+This was because the underlying Microsoft implementation does not
follow the standard. Perl now takes special precautions to correct for
this.
=item *
-system() and friends should now work properly on more Android builds.
+C<system()> and friends should now work properly on more Android builds.
Due to an oversight, the value specified through C<-Dtargetsh> to F<Configure>
would end up being ignored by some of the build process. This caused perls
cross-compiled for Android to end up with defective versions of C<system()>,
-exec() and backticks: the commands would end up looking for C</bin/sh>
+C<exec()> and backticks: the commands would end up looking for C</bin/sh>
instead of C</system/bin/sh>, and so would fail for the vast majority
of devices, leaving C<$!> as C<ENOENT>.
=item *
-C<< s///e >> on tainted utf8 strings got C<< pos() >> messed up. This bug,
+C<< s///e >> on tainted UTF-8 strings corrupted C<< pos() >>. This bug,
introduced in 5.20, is now fixed.
L<[perl #122148]|https://rt.perl.org/Ticket/Display.html?id=122148>.
=item *
-When parsing a funny character (C<$> C<@> C<%> C<&)> followed by braces,
+When parsing a sigil (C<$> C<@> C<%> C<&)> followed by braces,
the parser no
longer tries to guess whether it is a block or a hash constructor (causing a
syntax error when it guesses the latter), since it can only be a block.
=item *
-Under some conditions a warning raised in compilation of regular expression
-patterns could be displayed multiple times. This is now fixed.
+C<qr/[\N{named sequence}]/> now works properly in many instances.
-=item *
-
-C<qr/[\N{named sequence}]/> now works properly in many instances. Some names
+Some names
known to C<\N{...}> refer to a sequence of multiple characters, instead of the
usual single character. Bracketed character classes generally only match
single characters, but now special handling has been added so that they can
=item *
-S<C<open $$fh, ...>>, which vivifies a handle with a name like C<"main::_GEN_0">, was
-not giving the handle the right reference count, so a double free could happen.
+S<C<open $$fh, ...>>, which vivifies a handle with a name like
+C<"main::_GEN_0">, was not giving the handle the right reference count, so
+a double free could happen.
=item *
=item *
-A regression has been fixed that was introduced in Perl 5.20.0 (fixed in Perl
-5.20.1 as well as here) in which a UTF-8 encoded regular expression pattern
-that contains a single ASCII lowercase letter does not match its uppercase
-counterpart.
+Perl 5.20.0 introduced a regression in which a UTF-8 encoded regular
+expression pattern that contains a single ASCII lowercase letter did not
+match its uppercase counterpart. That has been fixed in both 5.20.1 and
+5.22.0.
L<[perl #122655]|https://rt.perl.org/Ticket/Display.html?id=122655>
=item *
-Constant folding could incorrectly suppress warnings if lexical warnings (C<use
-warnings> or C<no warnings>) were not in effect and C<$^W> were false at
-compile time and true at run time.
+Constant folding could incorrectly suppress warnings if lexical warnings
+(C<use warnings> or C<no warnings>) were not in effect and C<$^W> were
+false at compile time and true at run time.
=item *
-Loading UTF8 tables during a regular expression match could cause assertion
+Loading UTF-8 tables during a regular expression match could cause assertion
failures under debugging builds if the previous match used the very same
regular expression.
L<[perl #122747]|https://rt.perl.org/Ticket/Display.html?id=122747>
=item *
-S<C<(caller $n)[3]>> now reports names of lexical subs, instead of treating them
-as C<"(unknown)">.
+S<C<(caller $n)[3]>> now reports names of lexical subs, instead of
+treating them as C<"(unknown)">.
=item *
-C<sort subname LIST> now supports lexical subs for the comparison routine.
+C<sort subname LIST> now supports using a lexical sub as the comparison
+routine.
=item *
=item *
-An optimization in C<split> to treat C<split/^/> like C<split/^/m> had the
-unfortunate side-effect of also treating C<split/\A/> like C<split/^/m>, which
-it should not. This has been fixed. (Note, however, that C<split/^x/> does
-not behave like C<split/^x/m>, which is also considered to be a bug and will be
-fixed in a future version.)
+An optimization in C<split> to treat C<split /^/> like C<split /^/m> had the
+unfortunate side-effect of also treating C<split /\A/> like C<split /^/m>,
+which it should not. This has been fixed. (Note, however, that C<split /^x/>
+does not behave like C<split /^x/m>, which is also considered to be a bug and
+will be fixed in a future version.)
L<[perl #122761]|https://rt.perl.org/Ticket/Display.html?id=122761>
=item *
=item *
Locking and unlocking values via L<Hash::Util> or C<Internals::SvREADONLY>
-no longer has any effect on values that are read-only to begin.
+no longer has any effect on values that were read-only to begin with.
Previously, unlocking such values could result in crashes, hangs or
other erratic behaviour.
=item *
-The flip-flop operator (C<..> in scalar context) would return the same
-scalar each time, unless the containing subroutine was called recursively.
-Now it always returns a new scalar.
-L<[perl #122829]|https://rt.perl.org/Ticket/Display.html?id=122829>.
-
-=item *
-
Some unterminated C<(?(...)...)> constructs in regular expressions would
either crash or give erroneous error messages. C</(?(1)/> is one such
example.
=item *
In S<C<() = @array = split>>, the S<C<() =>> at the beginning no longer confuses
-the optimizer, making it assume a limit of 1.
+the optimizer into assuming a limit of 1.
=item *
=item *
-Fixed a NaN double to long double conversion error on VMS. For quiet NaNs
+Fixed a NaN double-to-long-double conversion error on VMS. For quiet NaNs
(and only on Itanium, not Alpha) negative infinity instead of NaN was
produced.
=item *
-Fixed the issue that caused C<< make distclean >> to leave files behind
-that shouldn't.
+Fixed the issue that caused C<< make distclean >> to incorrectly leave some
+files behind.
L<[perl #122820]|https://rt.perl.org/Ticket/Display.html?id=122820>.
=item *
=item *
-During the pattern optimization phase, we no longer recurse into
-C<GOSUB>/C<GOSTART> when not C<SCF_DO_SUBSTR>. This prevents the optimizer
-to run "forever" and exhaust all memory.
+During the optimization phase of a regexp compilation, we no longer
+recurse into C<GOSUB>/C<GOSTART> when the internal C<SCF_DO_SUBSTR> flag
+is false. This prevents the optimizer from running "forever" and
+exhausting all memory.
L<[perl #122283]|https://rt.perl.org/Ticket/Display.html?id=122283>.
=item *
-F<< t/op/crypt.t >> now performs SHA-256 algorithm if the default one
-is disabled.
+The test script F<< t/op/crypt.t >> now uses the SHA-256 algorithm if the
+default one is disabled, rather than giving failures.
L<[perl #121591]|https://rt.perl.org/Ticket/Display.html?id=121591>.
=item *
-Fixed an off-by-one error when setting the size of shared array.
+Fixed an off-by-one error when setting the size of a shared array.
L<[perl #122950]|https://rt.perl.org/Ticket/Display.html?id=122950>.
=item *
-Fixed a bug that could cause perl to execute an infinite loop during
-compilation.
+Fixed a bug that could cause perl to enter an infinite loop during
+compilation. In particular, for a C<while(1)> within a sublist, e.g.
+
+ sub foo { () = ($a, my $b, ($c, do { while(1) {} })) }
+
+The bug was introduced in 5.20.0
L<[perl #122995]|https://rt.perl.org/Ticket/Display.html?id=122995>.
=item *
-On Win32, restoring in a child pseudo-process a variable that was
-C<local()>ed in a parent pseudo-process before the C<fork> happened caused
-memory corruption and a crash in the child pseudo-process (and therefore OS
-process).
+On Win32, if a variable was C<local>-ized in a pseudo-process that later
+forked, restoring the original value in the child pseudo-process caused
+memory corruption and a crash in the child pseudo-process (and therefore the
+OS process).
L<[perl #40565]|https://rt.perl.org/Ticket/Display.html?id=40565>.
=item *
=item *
-Non-ASCII lexical sub names (use in error messages) on longer have extra
-junk on the end.
+Non-ASCII lexical sub names now appear without trailing junk when they
+appear in error messages.
=item *
=item *
In perl 5.20.0, C<sort CORE::fake> where 'fake' is anything other than a
-keyword started chopping of the last 6 characters and treating the result
+keyword, started chopping off the last 6 characters and treating the result
as a sort sub name. The previous behaviour of treating "CORE::fake" as a
sort sub name has been restored.
L<[perl #123410]|https://rt.perl.org/Ticket/Display.html?id=123410>.
=item *
-C<(...)x...> in void context now applies scalar context to the left-hand
+C<(...) x ...> in void context now applies scalar context to the left-hand
argument, instead of the context the current sub was called in.
L<[perl #123020]|https://rt.perl.org/Ticket/Display.html?id=123020>.
=item *
+C<pack>-ing a NaN on a perl compiled with Visual C 6 does not behave properly,
+leading to a test failure in F<t/op/infnan.t>.
+L<[perl 125203]|https://rt.perl.org/Ticket/Display.html?id=125203>
+
+=item *
+
A goal is for Perl to be able to be recompiled to work reasonably well on any
Unicode version. In Perl 5.22, though, the earliest such version is Unicode
5.1 (current is 7.0).
Ranges containing C<\N{...}> in the C<tr///> (and C<y///>)
transliteration operators are treated differently than the equivalent
-ranges in regular expression pattersn. They should, but don't, cause
+ranges in regular expression patterns. They should, but don't, cause
the values in the ranges to all be treated as Unicode code points, and
not native ones. (L<perlre/Version 8 Regular Expressions> gives
details as to how it should work.)
=back
-=head1 Acknowledgements
+=head1 Obituary
-XXX Generate this with:
+Brian McCauley died on May 8, 2015. He was a frequent poster to Usenet, Perl
+Monks, and other Perl forums, and made several CPAN contributions under the
+nick NOBULL, including to the Perl FAQ. He attended almost every
+YAPC::Europe, and indeed, helped organise YAPC::Europe 2006 and the QA
+Hackathon 2009. His wit and his delight in intricate systems were
+particularly apparent in his love of board games; many Perl mongers will
+have fond memories of playing Fluxx and other games with Brian. He will be
+missed.
+
+=head1 Acknowledgements
- perl Porting/acknowledgements.pl v5.20.0..HEAD
+Perl 5.22.0 represents approximately 12 months of development since Perl 5.20.0
+and contains approximately 590,000 lines of changes across 2,400 files from 94
+authors.
+
+Excluding auto-generated files, documentation and release tools, there were
+approximately 370,000 lines of changes to 1,500 .pm, .t, .c and .h files.
+
+Perl continues to flourish into its third decade thanks to a vibrant community
+of users and developers. The following people are known to have contributed the
+improvements that became Perl 5.22.0:
+
+Aaron Crane, Abhijit Menon-Sen, Abigail, Alberto Simões, Alex Solovey, Alex
+Vandiver, Alexandr Ciornii, Alexandre (Midnite) Jousset, Andreas König,
+Andreas Voegele, Andrew Fresh, Andy Dougherty, Anthony Heading, Aristotle
+Pagaltzis, brian d foy, Brian Fraser, Chad Granum, Chris 'BinGOs' Williams,
+Craig A. Berry, Dagfinn Ilmari Mannsåker, Daniel Dragan, Darin McBride, Dave
+Rolsky, David Golden, David Mitchell, David Wheeler, Dmitri Tikhonov, Doug
+Bell, E. Choroba, Ed J, Eric Herman, Father Chrysostomos, George Greer, Glenn
+D. Golden, Graham Knop, H.Merijn Brand, Herbert Breunung, Hugo van der Sanden,
+James E Keenan, James McCoy, James Raspass, Jan Dubois, Jarkko Hietaniemi,
+Jasmine Ngan, Jerry D. Hedden, Jim Cromie, John Goodyear, kafka, Karen
+Etheridge, Karl Williamson, Kent Fredric, kmx, Lajos Veres, Leon Timmermans,
+Lukas Mai, Mathieu Arnold, Matthew Horsfall, Max Maischein, Michael Bunk,
+Nicholas Clark, Niels Thykier, Niko Tyni, Norman Koch, Olivier Mengué, Peter
+John Acklam, Peter Martini, Petr Písař, Philippe Bruhat (BooK), Pierre
+Bogossian, Rafael Garcia-Suarez, Randy Stauner, Reini Urban, Ricardo Signes,
+Rob Hoelz, Rostislav Skudnov, Sawyer X, Shirakata Kentaro, Shlomi Fish,
+Sisyphus, Slaven Rezic, Smylers, Steffen Müller, Steve Hay, Sullivan Beck,
+syber, Tadeusz Sośnierz, Thomas Sibley, Todd Rinaldo, Tony Cook, Vincent Pit,
+Vladimir Marek, Yaroslav Kuzmin, Yves Orton, 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
https://perl5.git.perl.org / perl5.git / blobdiff