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-=encoding utf8
-
-=head1 NAME
-
-perl5100delta - what is new for perl 5.10.0
-
-=head1 DESCRIPTION
-
-This document describes the differences between the 5.8.8 release and
-the 5.10.0 release.
-
-Many of the bug fixes in 5.10.0 were already seen in the 5.8.X maintenance
-releases; they are not duplicated here and are documented in the set of
-man pages named perl58[1-8]?delta.
-
-=head1 Core Enhancements
-
-=head2 The C<feature> pragma
-
-The C<feature> pragma is used to enable new syntax that would break Perl's
-backwards-compatibility with older releases of the language. It's a lexical
-pragma, like C<strict> or C<warnings>.
-
-Currently the following new features are available: C<switch> (adds a
-switch statement), C<say> (adds a C<say> built-in function), and C<state>
-(adds a C<state> keyword for declaring "static" variables). Those
-features are described in their own sections of this document.
-
-The C<feature> pragma is also implicitly loaded when you require a minimal
-perl version (with the C<use VERSION> construct) greater than, or equal
-to, 5.9.5. See L<feature> for details.
-
-=head2 New B<-E> command-line switch
-
-B<-E> is equivalent to B<-e>, but it implicitly enables all
-optional features (like C<use feature ":5.10">).
-
-=head2 Defined-or operator
-
-A new operator C<//> (defined-or) has been implemented.
-The following expression:
-
- $a // $b
-
-is merely equivalent to
-
- defined $a ? $a : $b
-
-and the statement
-
- $c //= $d;
-
-can now be used instead of
-
- $c = $d unless defined $c;
-
-The C<//> operator has the same precedence and associativity as C<||>.
-Special care has been taken to ensure that this operator Do What You Mean
-while not breaking old code, but some edge cases involving the empty
-regular expression may now parse differently. See L<perlop> for
-details.
-
-=head2 Switch and Smart Match operator
-
-Perl 5 now has a switch statement. It's available when C<use feature
-'switch'> is in effect. This feature introduces three new keywords,
-C<given>, C<when>, and C<default>:
-
- given ($foo) {
- when (/^abc/) { $abc = 1; }
- when (/^def/) { $def = 1; }
- when (/^xyz/) { $xyz = 1; }
- default { $nothing = 1; }
- }
-
-A more complete description of how Perl matches the switch variable
-against the C<when> conditions is given in L<perlsyn/"Switch statements">.
-
-This kind of match is called I<smart match>, and it's also possible to use
-it outside of switch statements, via the new C<~~> operator. See
-L<perlsyn/"Smart matching in detail">.
-
-This feature was contributed by Robin Houston.
-
-=head2 Regular expressions
-
-=over 4
-
-=item Recursive Patterns
-
-It is now possible to write recursive patterns without using the C<(??{})>
-construct. This new way is more efficient, and in many cases easier to
-read.
-
-Each capturing parenthesis can now be treated as an independent pattern
-that can be entered by using the C<(?PARNO)> syntax (C<PARNO> standing for
-"parenthesis number"). For example, the following pattern will match
-nested balanced angle brackets:
-
- /
- ^ # start of line
- ( # start capture buffer 1
- < # match an opening angle bracket
- (?: # match one of:
- (?> # don't backtrack over the inside of this group
- [^<>]+ # one or more non angle brackets
- ) # end non backtracking group
- | # ... or ...
- (?1) # recurse to bracket 1 and try it again
- )* # 0 or more times.
- > # match a closing angle bracket
- ) # end capture buffer one
- $ # end of line
- /x
-
-PCRE users should note that Perl's recursive regex feature allows
-backtracking into a recursed pattern, whereas in PCRE the recursion is
-atomic or "possessive" in nature. As in the example above, you can
-add (?>) to control this selectively. (Yves Orton)
-
-=item Named Capture Buffers
-
-It is now possible to name capturing parenthesis in a pattern and refer to
-the captured contents by name. The naming syntax is C<< (?<NAME>....) >>.
-It's possible to backreference to a named buffer with the C<< \k<NAME> >>
-syntax. In code, the new magical hashes C<%+> and C<%-> can be used to
-access the contents of the capture buffers.
-
-Thus, to replace all doubled chars with a single copy, one could write
-
- s/(?<letter>.)\k<letter>/$+{letter}/g
-
-Only buffers with defined contents will be "visible" in the C<%+> hash, so
-it's possible to do something like
-
- foreach my $name (keys %+) {
- print "content of buffer '$name' is $+{$name}\n";
- }
-
-The C<%-> hash is a bit more complete, since it will contain array refs
-holding values from all capture buffers similarly named, if there should
-be many of them.
-
-C<%+> and C<%-> are implemented as tied hashes through the new module
-C<Tie::Hash::NamedCapture>.
-
-Users exposed to the .NET regex engine will find that the perl
-implementation differs in that the numerical ordering of the buffers
-is sequential, and not "unnamed first, then named". Thus in the pattern
-
- /(A)(?<B>B)(C)(?<D>D)/
-
-$1 will be 'A', $2 will be 'B', $3 will be 'C' and $4 will be 'D' and not
-$1 is 'A', $2 is 'C' and $3 is 'B' and $4 is 'D' that a .NET programmer
-would expect. This is considered a feature. :-) (Yves Orton)
-
-=item Possessive Quantifiers
-
-Perl now supports the "possessive quantifier" syntax of the "atomic match"
-pattern. Basically a possessive quantifier matches as much as it can and never
-gives any back. Thus it can be used to control backtracking. The syntax is
-similar to non-greedy matching, except instead of using a '?' as the modifier
-the '+' is used. Thus C<?+>, C<*+>, C<++>, C<{min,max}+> are now legal
-quantifiers. (Yves Orton)
-
-=item Backtracking control verbs
-
-The regex engine now supports a number of special-purpose backtrack
-control verbs: (*THEN), (*PRUNE), (*MARK), (*SKIP), (*COMMIT), (*FAIL)
-and (*ACCEPT). See L<perlre> for their descriptions. (Yves Orton)
-
-=item Relative backreferences
-
-A new syntax C<\g{N}> or C<\gN> where "N" is a decimal integer allows a
-safer form of back-reference notation as well as allowing relative
-backreferences. This should make it easier to generate and embed patterns
-that contain backreferences. See L<perlre/"Capture buffers">. (Yves Orton)
-
-=item C<\K> escape
-
-The functionality of Jeff Pinyan's module Regexp::Keep has been added to
-the core. In regular expressions you can now use the special escape C<\K>
-as a way to do something like floating length positive lookbehind. It is
-also useful in substitutions like:
-
- s/(foo)bar/$1/g
-
-that can now be converted to
-
- s/foo\Kbar//g
-
-which is much more efficient. (Yves Orton)
-
-=item Vertical and horizontal whitespace, and linebreak
-
-Regular expressions now recognize the C<\v> and C<\h> escapes that match
-vertical and horizontal whitespace, respectively. C<\V> and C<\H>
-logically match their complements.
-
-C<\R> matches a generic linebreak, that is, vertical whitespace, plus
-the multi-character sequence C<"\x0D\x0A">.
-
-=back
-
-=head2 C<say()>
-
-say() is a new built-in, only available when C<use feature 'say'> is in
-effect, that is similar to print(), but that implicitly appends a newline
-to the printed string. See L<perlfunc/say>. (Robin Houston)
-
-=head2 Lexical C<$_>
-
-The default variable C<$_> can now be lexicalized, by declaring it like
-any other lexical variable, with a simple
-
- my $_;
-
-The operations that default on C<$_> will use the lexically-scoped
-version of C<$_> when it exists, instead of the global C<$_>.
-
-In a C<map> or a C<grep> block, if C<$_> was previously my'ed, then the
-C<$_> inside the block is lexical as well (and scoped to the block).
-
-In a scope where C<$_> has been lexicalized, you can still have access to
-the global version of C<$_> by using C<$::_>, or, more simply, by
-overriding the lexical declaration with C<our $_>. (Rafael Garcia-Suarez)
-
-=head2 The C<_> prototype
-
-A new prototype character has been added. C<_> is equivalent to C<$> but
-defaults to C<$_> if the corresponding argument isn't supplied (both C<$>
-and C<_> denote a scalar). Due to the optional nature of the argument,
-you can only use it at the end of a prototype, or before a semicolon.
-
-This has a small incompatible consequence: the prototype() function has
-been adjusted to return C<_> for some built-ins in appropriate cases (for
-example, C<prototype('CORE::rmdir')>). (Rafael Garcia-Suarez)
-
-=head2 UNITCHECK blocks
-
-C<UNITCHECK>, a new special code block has been introduced, in addition to
-C<BEGIN>, C<CHECK>, C<INIT> and C<END>.
-
-C<CHECK> and C<INIT> blocks, while useful for some specialized purposes,
-are always executed at the transition between the compilation and the
-execution of the main program, and thus are useless whenever code is
-loaded at runtime. On the other hand, C<UNITCHECK> blocks are executed
-just after the unit which defined them has been compiled. See L<perlmod>
-for more information. (Alex Gough)
-
-=head2 New Pragma, C<mro>
-
-A new pragma, C<mro> (for Method Resolution Order) has been added. It
-permits to switch, on a per-class basis, the algorithm that perl uses to
-find inherited methods in case of a multiple inheritance hierarchy. The
-default MRO hasn't changed (DFS, for Depth First Search). Another MRO is
-available: the C3 algorithm. See L<mro> for more information.
-(Brandon Black)
-
-Note that, due to changes in the implementation of class hierarchy search,
-code that used to undef the C<*ISA> glob will most probably break. Anyway,
-undef'ing C<*ISA> had the side-effect of removing the magic on the @ISA
-array and should not have been done in the first place. Also, the
-cache C<*::ISA::CACHE::> no longer exists; to force reset the @ISA cache,
-you now need to use the C<mro> API, or more simply to assign to @ISA
-(e.g. with C<@ISA = @ISA>).
-
-=head2 readdir() may return a "short filename" on Windows
-
-The readdir() function may return a "short filename" when the long
-filename contains characters outside the ANSI codepage. Similarly
-Cwd::cwd() may return a short directory name, and glob() may return short
-names as well. On the NTFS file system these short names can always be
-represented in the ANSI codepage. This will not be true for all other file
-system drivers; e.g. the FAT filesystem stores short filenames in the OEM
-codepage, so some files on FAT volumes remain unaccessible through the
-ANSI APIs.
-
-Similarly, $^X, @INC, and $ENV{PATH} are preprocessed at startup to make
-sure all paths are valid in the ANSI codepage (if possible).
-
-The Win32::GetLongPathName() function now returns the UTF-8 encoded
-correct long file name instead of using replacement characters to force
-the name into the ANSI codepage. The new Win32::GetANSIPathName()
-function can be used to turn a long pathname into a short one only if the
-long one cannot be represented in the ANSI codepage.
-
-Many other functions in the C<Win32> module have been improved to accept
-UTF-8 encoded arguments. Please see L<Win32> for details.
-
-=head2 readpipe() is now overridable
-
-The built-in function readpipe() is now overridable. Overriding it permits
-also to override its operator counterpart, C<qx//> (a.k.a. C<``>).
-Moreover, it now defaults to C<$_> if no argument is provided. (Rafael
-Garcia-Suarez)
-
-=head2 Default argument for readline()
-
-readline() now defaults to C<*ARGV> if no argument is provided. (Rafael
-Garcia-Suarez)
-
-=head2 state() variables
-
-A new class of variables has been introduced. State variables are similar
-to C<my> variables, but are declared with the C<state> keyword in place of
-C<my>. They're visible only in their lexical scope, but their value is
-persistent: unlike C<my> variables, they're not undefined at scope entry,
-but retain their previous value. (Rafael Garcia-Suarez, Nicholas Clark)
-
-To use state variables, one needs to enable them by using
-
- use feature 'state';
-
-or by using the C<-E> command-line switch in one-liners.
-See L<perlsub/"Persistent Private Variables">.
-
-=head2 Stacked filetest operators
-
-As a new form of syntactic sugar, it's now possible to stack up filetest
-operators. You can now write C<-f -w -x $file> in a row to mean
-C<-x $file && -w _ && -f _>. See L<perlfunc/-X>.
-
-=head2 UNIVERSAL::DOES()
-
-The C<UNIVERSAL> class has a new method, C<DOES()>. It has been added to
-solve semantic problems with the C<isa()> method. C<isa()> checks for
-inheritance, while C<DOES()> has been designed to be overridden when
-module authors use other types of relations between classes (in addition
-to inheritance). (chromatic)
-
-See L<< UNIVERSAL/"$obj->DOES( ROLE )" >>.
-
-=head2 Formats
-
-Formats were improved in several ways. A new field, C<^*>, can be used for
-variable-width, one-line-at-a-time text. Null characters are now handled
-correctly in picture lines. Using C<@#> and C<~~> together will now
-produce a compile-time error, as those format fields are incompatible.
-L<perlform> has been improved, and miscellaneous bugs fixed.
-
-=head2 Byte-order modifiers for pack() and unpack()
-
-There are two new byte-order modifiers, C<E<gt>> (big-endian) and C<E<lt>>
-(little-endian), that can be appended to most pack() and unpack() template
-characters and groups to force a certain byte-order for that type or group.
-See L<perlfunc/pack> and L<perlpacktut> for details.
-
-=head2 C<no VERSION>
-
-You can now use C<no> followed by a version number to specify that you
-want to use a version of perl older than the specified one.
-
-=head2 C<chdir>, C<chmod> and C<chown> on filehandles
-
-C<chdir>, C<chmod> and C<chown> can now work on filehandles as well as
-filenames, if the system supports respectively C<fchdir>, C<fchmod> and
-C<fchown>, thanks to a patch provided by Gisle Aas.
-
-=head2 OS groups
-
-C<$(> and C<$)> now return groups in the order where the OS returns them,
-thanks to Gisle Aas. This wasn't previously the case.
-
-=head2 Recursive sort subs
-
-You can now use recursive subroutines with sort(), thanks to Robin Houston.
-
-=head2 Exceptions in constant folding
-
-The constant folding routine is now wrapped in an exception handler, and
-if folding throws an exception (such as attempting to evaluate 0/0), perl
-now retains the current optree, rather than aborting the whole program.
-Without this change, programs would not compile if they had expressions that
-happened to generate exceptions, even though those expressions were in code
-that could never be reached at runtime. (Nicholas Clark, Dave Mitchell)
-
-=head2 Source filters in @INC
-
-It's possible to enhance the mechanism of subroutine hooks in @INC by
-adding a source filter on top of the filehandle opened and returned by the
-hook. This feature was planned a long time ago, but wasn't quite working
-until now. See L<perlfunc/require> for details. (Nicholas Clark)
-
-=head2 New internal variables
-
-=over 4
-
-=item C<${^RE_DEBUG_FLAGS}>
-
-This variable controls what debug flags are in effect for the regular
-expression engine when running under C<use re "debug">. See L<re> for
-details.
-
-=item C<${^CHILD_ERROR_NATIVE}>
-
-This variable gives the native status returned by the last pipe close,
-backtick command, successful call to wait() or waitpid(), or from the
-system() operator. See L<perlvar> for details. (Contributed by Gisle Aas.)
-
-=item C<${^RE_TRIE_MAXBUF}>
-
-See L</"Trie optimisation of literal string alternations">.
-
-=item C<${^WIN32_SLOPPY_STAT}>
-
-See L</"Sloppy stat on Windows">.
-
-=back
-
-=head2 Miscellaneous
-
-C<unpack()> now defaults to unpacking the C<$_> variable.
-
-C<mkdir()> without arguments now defaults to C<$_>.
-
-The internal dump output has been improved, so that non-printable characters
-such as newline and backspace are output in C<\x> notation, rather than
-octal.
-
-The B<-C> option can no longer be used on the C<#!> line. It wasn't
-working there anyway, since the standard streams are already set up
-at this point in the execution of the perl interpreter. You can use
-binmode() instead to get the desired behaviour.
-
-=head2 UCD 5.0.0
-
-The copy of the Unicode Character Database included in Perl 5 has
-been updated to version 5.0.0.
-
-=head2 MAD
-
-MAD, which stands for I<Miscellaneous Attribute Decoration>, is a
-still-in-development work leading to a Perl 5 to Perl 6 converter. To
-enable it, it's necessary to pass the argument C<-Dmad> to Configure. The
-obtained perl isn't binary compatible with a regular perl 5.10, and has
-space and speed penalties; moreover not all regression tests still pass
-with it. (Larry Wall, Nicholas Clark)
-
-=head2 kill() on Windows
-
-On Windows platforms, C<kill(-9, $pid)> now kills a process tree.
-(On Unix, this delivers the signal to all processes in the same process
-group.)
-
-=head1 Incompatible Changes
-
-=head2 Packing and UTF-8 strings
-
-The semantics of pack() and unpack() regarding UTF-8-encoded data has been
-changed. Processing is now by default character per character instead of
-byte per byte on the underlying encoding. Notably, code that used things
-like C<pack("a*", $string)> to see through the encoding of string will now
-simply get back the original $string. Packed strings can also get upgraded
-during processing when you store upgraded characters. You can get the old
-behaviour by using C<use bytes>.
-
-To be consistent with pack(), the C<C0> in unpack() templates indicates
-that the data is to be processed in character mode, i.e. character by
-character; on the contrary, C<U0> in unpack() indicates UTF-8 mode, where
-the packed string is processed in its UTF-8-encoded Unicode form on a byte
-by byte basis. This is reversed with regard to perl 5.8.X, but now consistent
-between pack() and unpack().
-
-Moreover, C<C0> and C<U0> can also be used in pack() templates to specify
-respectively character and byte modes.
-
-C<C0> and C<U0> in the middle of a pack or unpack format now switch to the
-specified encoding mode, honoring parens grouping. Previously, parens were
-ignored.
-
-Also, there is a new pack() character format, C<W>, which is intended to
-replace the old C<C>. C<C> is kept for unsigned chars coded as bytes in
-the strings internal representation. C<W> represents unsigned (logical)
-character values, which can be greater than 255. It is therefore more
-robust when dealing with potentially UTF-8-encoded data (as C<C> will wrap
-values outside the range 0..255, and not respect the string encoding).
-
-In practice, that means that pack formats are now encoding-neutral, except
-C<C>.
-
-For consistency, C<A> in unpack() format now trims all Unicode whitespace
-from the end of the string. Before perl 5.9.2, it used to strip only the
-classical ASCII space characters.
-
-=head2 Byte/character count feature in unpack()
-
-A new unpack() template character, C<".">, returns the number of bytes or
-characters (depending on the selected encoding mode, see above) read so far.
-
-=head2 The C<$*> and C<$#> variables have been removed
-
-C<$*>, which was deprecated in favor of the C</s> and C</m> regexp
-modifiers, has been removed.
-
-The deprecated C<$#> variable (output format for numbers) has been
-removed.
-
-Two new severe warnings, C<$#/$* is no longer supported>, have been added.
-
-=head2 substr() lvalues are no longer fixed-length
-
-The lvalues returned by the three argument form of substr() used to be a
-"fixed length window" on the original string. In some cases this could
-cause surprising action at distance or other undefined behaviour. Now the
-length of the window adjusts itself to the length of the string assigned to
-it.
-
-=head2 Parsing of C<-f _>
-
-The identifier C<_> is now forced to be a bareword after a filetest
-operator. This solves a number of misparsing issues when a global C<_>
-subroutine is defined.
-
-=head2 C<:unique>
-
-The C<:unique> attribute has been made a no-op, since its current
-implementation was fundamentally flawed and not threadsafe.
-
-=head2 Effect of pragmas in eval
-
-The compile-time value of the C<%^H> hint variable can now propagate into
-eval("")uated code. This makes it more useful to implement lexical
-pragmas.
-
-As a side-effect of this, the overloaded-ness of constants now propagates
-into eval("").
-
-=head2 chdir FOO
-
-A bareword argument to chdir() is now recognized as a file handle.
-Earlier releases interpreted the bareword as a directory name.
-(Gisle Aas)
-
-=head2 Handling of .pmc files
-
-An old feature of perl was that before C<require> or C<use> look for a
-file with a F<.pm> extension, they will first look for a similar filename
-with a F<.pmc> extension. If this file is found, it will be loaded in
-place of any potentially existing file ending in a F<.pm> extension.
-
-Previously, F<.pmc> files were loaded only if more recent than the
-matching F<.pm> file. Starting with 5.9.4, they'll be always loaded if
-they exist.
-
-=head2 $^V is now a C<version> object instead of a v-string
-
-$^V can still be used with the C<%vd> format in printf, but any
-character-level operations will now access the string representation
-of the C<version> object and not the ordinals of a v-string.
-Expressions like C<< substr($^V, 0, 2) >> or C<< split //, $^V >>
-no longer work and must be rewritten.
-
-=head2 @- and @+ in patterns
-
-The special arrays C<@-> and C<@+> are no longer interpolated in regular
-expressions. (Sadahiro Tomoyuki)
-
-=head2 $AUTOLOAD can now be tainted
-
-If you call a subroutine by a tainted name, and if it defers to an
-AUTOLOAD function, then $AUTOLOAD will be (correctly) tainted.
-(Rick Delaney)
-
-=head2 Tainting and printf
-
-When perl is run under taint mode, C<printf()> and C<sprintf()> will now
-reject any tainted format argument. (Rafael Garcia-Suarez)
-
-=head2 undef and signal handlers
-
-Undefining or deleting a signal handler via C<undef $SIG{FOO}> is now
-equivalent to setting it to C<'DEFAULT'>. (Rafael Garcia-Suarez)
-
-=head2 strictures and dereferencing in defined()
-
-C<use strict 'refs'> was ignoring taking a hard reference in an argument
-to defined(), as in :
-
- use strict 'refs';
- my $x = 'foo';
- if (defined $$x) {...}
-
-This now correctly produces the run-time error C<Can't use string as a
-SCALAR ref while "strict refs" in use>.
-
-C<defined @$foo> and C<defined %$bar> are now also subject to C<strict
-'refs'> (that is, C<$foo> and C<$bar> shall be proper references there.)
-(C<defined(@foo)> and C<defined(%bar)> are discouraged constructs anyway.)
-(Nicholas Clark)
-
-=head2 C<(?p{})> has been removed
-
-The regular expression construct C<(?p{})>, which was deprecated in perl
-5.8, has been removed. Use C<(??{})> instead. (Rafael Garcia-Suarez)
-
-=head2 Pseudo-hashes have been removed
-
-Support for pseudo-hashes has been removed from Perl 5.9. (The C<fields>
-pragma remains here, but uses an alternate implementation.)
-
-=head2 Removal of the bytecode compiler and of perlcc
-
-C<perlcc>, the byteloader and the supporting modules (B::C, B::CC,
-B::Bytecode, etc.) are no longer distributed with the perl sources. Those
-experimental tools have never worked reliably, and, due to the lack of
-volunteers to keep them in line with the perl interpreter developments, it
-was decided to remove them instead of shipping a broken version of those.
-The last version of those modules can be found with perl 5.9.4.
-
-However the B compiler framework stays supported in the perl core, as with
-the more useful modules it has permitted (among others, B::Deparse and
-B::Concise).
-
-=head2 Removal of the JPL
-
-The JPL (Java-Perl Lingo) has been removed from the perl sources tarball.
-
-=head2 Recursive inheritance detected earlier
-
-Perl will now immediately throw an exception if you modify any package's
-C<@ISA> in such a way that it would cause recursive inheritance.
-
-Previously, the exception would not occur until Perl attempted to make
-use of the recursive inheritance while resolving a method or doing a
-C<$foo-E<gt>isa($bar)> lookup.
-
-=head2 warnings::enabled and warnings::warnif changed to favor users of modules
-
-The behaviour in 5.10.x favors the person using the module;
-The behaviour in 5.8.x favors the module writer;
-
-Assume the following code:
-
- main calls Foo::Bar::baz()
- Foo::Bar inherits from Foo::Base
- Foo::Bar::baz() calls Foo::Base::_bazbaz()
- Foo::Base::_bazbaz() calls: warnings::warnif('substr', 'some warning
-message');
-
-On 5.8.x, the code warns when Foo::Bar contains C<use warnings;>
-It does not matter if Foo::Base or main have warnings enabled
-to disable the warning one has to modify Foo::Bar.
-
-On 5.10.0 and newer, the code warns when main contains C<use warnings;>
-It does not matter if Foo::Base or Foo::Bar have warnings enabled
-to disable the warning one has to modify main.
-
-=head1 Modules and Pragmata
-
-=head2 Upgrading individual core modules
-
-Even more core modules are now also available separately through the
-CPAN. If you wish to update one of these modules, you don't need to
-wait for a new perl release. From within the cpan shell, running the
-'r' command will report on modules with upgrades available. See
-C<perldoc CPAN> for more information.
-
-=head2 Pragmata Changes
-
-=over 4
-
-=item C<feature>
-
-The new pragma C<feature> is used to enable new features that might break
-old code. See L</"The C<feature> pragma"> above.
-
-=item C<mro>
-
-This new pragma enables to change the algorithm used to resolve inherited
-methods. See L</"New Pragma, C<mro>"> above.
-
-=item Scoping of the C<sort> pragma
-
-The C<sort> pragma is now lexically scoped. Its effect used to be global.
-
-=item Scoping of C<bignum>, C<bigint>, C<bigrat>
-
-The three numeric pragmas C<bignum>, C<bigint> and C<bigrat> are now
-lexically scoped. (Tels)
-
-=item C<base>
-
-The C<base> pragma now warns if a class tries to inherit from itself.
-(Curtis "Ovid" Poe)
-
-=item C<strict> and C<warnings>
-
-C<strict> and C<warnings> will now complain loudly if they are loaded via
-incorrect casing (as in C<use Strict;>). (Johan Vromans)
-
-=item C<version>
-
-The C<version> module provides support for version objects.
-
-=item C<warnings>
-
-The C<warnings> pragma doesn't load C<Carp> anymore. That means that code
-that used C<Carp> routines without having loaded it at compile time might
-need to be adjusted; typically, the following (faulty) code won't work
-anymore, and will require parentheses to be added after the function name:
-
- use warnings;
- require Carp;
- Carp::confess 'argh';
-
-=item C<less>
-
-C<less> now does something useful (or at least it tries to). In fact, it
-has been turned into a lexical pragma. So, in your modules, you can now
-test whether your users have requested to use less CPU, or less memory,
-less magic, or maybe even less fat. See L<less> for more. (Joshua ben
-Jore)
-
-=back
-
-=head2 New modules
-
-=over 4
-
-=item *
-
-C<encoding::warnings>, by Audrey Tang, is a module to emit warnings
-whenever an ASCII character string containing high-bit bytes is implicitly
-converted into UTF-8. It's a lexical pragma since Perl 5.9.4; on older
-perls, its effect is global.
-
-=item *
-
-C<Module::CoreList>, by Richard Clamp, is a small handy module that tells
-you what versions of core modules ship with any versions of Perl 5. It
-comes with a command-line frontend, C<corelist>.
-
-=item *
-
-C<Math::BigInt::FastCalc> is an XS-enabled, and thus faster, version of
-C<Math::BigInt::Calc>.
-
-=item *
-
-C<Compress::Zlib> is an interface to the zlib compression library. It
-comes with a bundled version of zlib, so having a working zlib is not a
-prerequisite to install it. It's used by C<Archive::Tar> (see below).
-
-=item *
-
-C<IO::Zlib> is an C<IO::>-style interface to C<Compress::Zlib>.
-
-=item *
-
-C<Archive::Tar> is a module to manipulate C<tar> archives.
-
-=item *
-
-C<Digest::SHA> is a module used to calculate many types of SHA digests,
-has been included for SHA support in the CPAN module.
-
-=item *
-
-C<ExtUtils::CBuilder> and C<ExtUtils::ParseXS> have been added.
-
-=item *
-
-C<Hash::Util::FieldHash>, by Anno Siegel, has been added. This module
-provides support for I<field hashes>: hashes that maintain an association
-of a reference with a value, in a thread-safe garbage-collected way.
-Such hashes are useful to implement inside-out objects.
-
-=item *
-
-C<Module::Build>, by Ken Williams, has been added. It's an alternative to
-C<ExtUtils::MakeMaker> to build and install perl modules.
-
-=item *
-
-C<Module::Load>, by Jos Boumans, has been added. It provides a single
-interface to load Perl modules and F<.pl> files.
-
-=item *
-
-C<Module::Loaded>, by Jos Boumans, has been added. It's used to mark
-modules as loaded or unloaded.
-
-=item *
-
-C<Package::Constants>, by Jos Boumans, has been added. It's a simple
-helper to list all constants declared in a given package.
-
-=item *
-
-C<Win32API::File>, by Tye McQueen, has been added (for Windows builds).
-This module provides low-level access to Win32 system API calls for
-files/dirs.
-
-=item *
-
-C<Locale::Maketext::Simple>, needed by CPANPLUS, is a simple wrapper around
-C<Locale::Maketext::Lexicon>. Note that C<Locale::Maketext::Lexicon> isn't
-included in the perl core; the behaviour of C<Locale::Maketext::Simple>
-gracefully degrades when the later isn't present.
-
-=item *
-
-C<Params::Check> implements a generic input parsing/checking mechanism. It
-is used by CPANPLUS.
-
-=item *
-
-C<Term::UI> simplifies the task to ask questions at a terminal prompt.
-
-=item *
-
-C<Object::Accessor> provides an interface to create per-object accessors.
-
-=item *
-
-C<Module::Pluggable> is a simple framework to create modules that accept
-pluggable sub-modules.
-
-=item *
-
-C<Module::Load::Conditional> provides simple ways to query and possibly
-load installed modules.
-
-=item *
-
-C<Time::Piece> provides an object oriented interface to time functions,
-overriding the built-ins localtime() and gmtime().
-
-=item *
-
-C<IPC::Cmd> helps to find and run external commands, possibly
-interactively.
-
-=item *
-
-C<File::Fetch> provide a simple generic file fetching mechanism.
-
-=item *
-
-C<Log::Message> and C<Log::Message::Simple> are used by the log facility
-of C<CPANPLUS>.
-
-=item *
-
-C<Archive::Extract> is a generic archive extraction mechanism
-for F<.tar> (plain, gzipped or bzipped) or F<.zip> files.
-
-=item *
-
-C<CPANPLUS> provides an API and a command-line tool to access the CPAN
-mirrors.
-
-=item *
-
-C<Pod::Escapes> provides utilities that are useful in decoding Pod
-EE<lt>...E<gt> sequences.
-
-=item *
-
-C<Pod::Simple> is now the backend for several of the Pod-related modules
-included with Perl.
-
-=back
-
-=head2 Selected Changes to Core Modules
-
-=over 4
-
-=item C<Attribute::Handlers>
-
-C<Attribute::Handlers> can now report the caller's file and line number.
-(David Feldman)
-
-All interpreted attributes are now passed as array references. (Damian
-Conway)
-
-=item C<B::Lint>
-
-C<B::Lint> is now based on C<Module::Pluggable>, and so can be extended
-with plugins. (Joshua ben Jore)
-
-=item C<B>
-
-It's now possible to access the lexical pragma hints (C<%^H>) by using the
-method B::COP::hints_hash(). It returns a C<B::RHE> object, which in turn
-can be used to get a hash reference via the method B::RHE::HASH(). (Joshua
-ben Jore)
-
-=item C<Thread>
-
-As the old 5005thread threading model has been removed, in favor of the
-ithreads scheme, the C<Thread> module is now a compatibility wrapper, to
-be used in old code only. It has been removed from the default list of
-dynamic extensions.
-
-=back
-
-=head1 Utility Changes
-
-=over 4
-
-=item perl -d
-
-The Perl debugger can now save all debugger commands for sourcing later;
-notably, it can now emulate stepping backwards, by restarting and
-rerunning all bar the last command from a saved command history.
-
-It can also display the parent inheritance tree of a given class, with the
-C<i> command.
-
-=item ptar
-
-C<ptar> is a pure perl implementation of C<tar> that comes with
-C<Archive::Tar>.
-
-=item ptardiff
-
-C<ptardiff> is a small utility used to generate a diff between the contents
-of a tar archive and a directory tree. Like C<ptar>, it comes with
-C<Archive::Tar>.
-
-=item shasum
-
-C<shasum> is a command-line utility, used to print or to check SHA
-digests. It comes with the new C<Digest::SHA> module.
-
-=item corelist
-
-The C<corelist> utility is now installed with perl (see L</"New modules">
-above).
-
-=item h2ph and h2xs
-
-C<h2ph> and C<h2xs> have been made more robust with regard to
-"modern" C code.
-
-C<h2xs> implements a new option C<--use-xsloader> to force use of
-C<XSLoader> even in backwards compatible modules.
-
-The handling of authors' names that had apostrophes has been fixed.
-
-Any enums with negative values are now skipped.
-
-=item perlivp
-
-C<perlivp> no longer checks for F<*.ph> files by default. Use the new C<-a>
-option to run I<all> tests.
-
-=item find2perl
-
-C<find2perl> now assumes C<-print> as a default action. Previously, it
-needed to be specified explicitly.
-
-Several bugs have been fixed in C<find2perl>, regarding C<-exec> and
-C<-eval>. Also the options C<-path>, C<-ipath> and C<-iname> have been
-added.
-
-=item config_data
-
-C<config_data> is a new utility that comes with C<Module::Build>. It
-provides a command-line interface to the configuration of Perl modules
-that use Module::Build's framework of configurability (that is,
-C<*::ConfigData> modules that contain local configuration information for
-their parent modules.)
-
-=item cpanp
-
-C<cpanp>, the CPANPLUS shell, has been added. (C<cpanp-run-perl>, a
-helper for CPANPLUS operation, has been added too, but isn't intended for
-direct use).
-
-=item cpan2dist
-
-C<cpan2dist> is a new utility that comes with CPANPLUS. It's a tool to
-create distributions (or packages) from CPAN modules.
-
-=item pod2html
-
-The output of C<pod2html> has been enhanced to be more customizable via
-CSS. Some formatting problems were also corrected. (Jari Aalto)
-
-=back
-
-=head1 New Documentation
-
-The L<perlpragma> manpage documents how to write one's own lexical
-pragmas in pure Perl (something that is possible starting with 5.9.4).
-
-The new L<perlglossary> manpage is a glossary of terms used in the Perl
-documentation, technical and otherwise, kindly provided by O'Reilly Media,
-Inc.
-
-The L<perlreguts> manpage, courtesy of Yves Orton, describes internals of the
-Perl regular expression engine.
-
-The L<perlreapi> manpage describes the interface to the perl interpreter
-used to write pluggable regular expression engines (by Ævar Arnfjörð
-Bjarmason).
-
-The L<perlunitut> manpage is an tutorial for programming with Unicode and
-string encodings in Perl, courtesy of Juerd Waalboer.
-
-A new manual page, L<perlunifaq> (the Perl Unicode FAQ), has been added
-(Juerd Waalboer).
-
-The L<perlcommunity> manpage gives a description of the Perl community
-on the Internet and in real life. (Edgar "Trizor" Bering)
-
-The L<CORE> manual page documents the C<CORE::> namespace. (Tels)
-
-The long-existing feature of C</(?{...})/> regexps setting C<$_> and pos()
-is now documented.
-
-=head1 Performance Enhancements
-
-=head2 In-place sorting
-
-Sorting arrays in place (C<@a = sort @a>) is now optimized to avoid
-making a temporary copy of the array.
-
-Likewise, C<reverse sort ...> is now optimized to sort in reverse,
-avoiding the generation of a temporary intermediate list.
-
-=head2 Lexical array access
-
-Access to elements of lexical arrays via a numeric constant between 0 and
-255 is now faster. (This used to be only the case for global arrays.)
-
-=head2 XS-assisted SWASHGET
-
-Some pure-perl code that perl was using to retrieve Unicode properties and
-transliteration mappings has been reimplemented in XS.
-
-=head2 Constant subroutines
-
-The interpreter internals now support a far more memory efficient form of
-inlineable constants. Storing a reference to a constant value in a symbol
-table is equivalent to a full typeglob referencing a constant subroutine,
-but using about 400 bytes less memory. This proxy constant subroutine is
-automatically upgraded to a real typeglob with subroutine if necessary.
-The approach taken is analogous to the existing space optimisation for
-subroutine stub declarations, which are stored as plain scalars in place
-of the full typeglob.
-
-Several of the core modules have been converted to use this feature for
-their system dependent constants - as a result C<use POSIX;> now takes about
-200K less memory.
-
-=head2 C<PERL_DONT_CREATE_GVSV>
-
-The new compilation flag C<PERL_DONT_CREATE_GVSV>, introduced as an option
-in perl 5.8.8, is turned on by default in perl 5.9.3. It prevents perl
-from creating an empty scalar with every new typeglob. See L<perl589delta>
-for details.
-
-=head2 Weak references are cheaper
-
-Weak reference creation is now I<O(1)> rather than I<O(n)>, courtesy of
-Nicholas Clark. Weak reference deletion remains I<O(n)>, but if deletion only
-happens at program exit, it may be skipped completely.
-
-=head2 sort() enhancements
-
-Salvador Fandiño provided improvements to reduce the memory usage of C<sort>
-and to speed up some cases.
-
-=head2 Memory optimisations
-
-Several internal data structures (typeglobs, GVs, CVs, formats) have been
-restructured to use less memory. (Nicholas Clark)
-
-=head2 UTF-8 cache optimisation
-
-The UTF-8 caching code is now more efficient, and used more often.
-(Nicholas Clark)
-
-=head2 Sloppy stat on Windows
-
-On Windows, perl's stat() function normally opens the file to determine
-the link count and update attributes that may have been changed through
-hard links. Setting ${^WIN32_SLOPPY_STAT} to a true value speeds up
-stat() by not performing this operation. (Jan Dubois)
-
-=head2 Regular expressions optimisations
-
-=over 4
-
-=item Engine de-recursivised
-
-The regular expression engine is no longer recursive, meaning that
-patterns that used to overflow the stack will either die with useful
-explanations, or run to completion, which, since they were able to blow
-the stack before, will likely take a very long time to happen. If you were
-experiencing the occasional stack overflow (or segfault) and upgrade to
-discover that now perl apparently hangs instead, look for a degenerate
-regex. (Dave Mitchell)
-
-=item Single char char-classes treated as literals
-
-Classes of a single character are now treated the same as if the character
-had been used as a literal, meaning that code that uses char-classes as an
-escaping mechanism will see a speedup. (Yves Orton)
-
-=item Trie optimisation of literal string alternations
-
-Alternations, where possible, are optimised into more efficient matching
-structures. String literal alternations are merged into a trie and are
-matched simultaneously. This means that instead of O(N) time for matching
-N alternations at a given point, the new code performs in O(1) time.
-A new special variable, ${^RE_TRIE_MAXBUF}, has been added to fine-tune
-this optimization. (Yves Orton)
-
-B<Note:> Much code exists that works around perl's historic poor
-performance on alternations. Often the tricks used to do so will disable
-the new optimisations. Hopefully the utility modules used for this purpose
-will be educated about these new optimisations.
-
-=item Aho-Corasick start-point optimisation
-
-When a pattern starts with a trie-able alternation and there aren't
-better optimisations available, the regex engine will use Aho-Corasick
-matching to find the start point. (Yves Orton)
-
-=back
-
-=head1 Installation and Configuration Improvements
-
-=head2 Configuration improvements
-
-=over 4
-
-=item C<-Dusesitecustomize>
-
-Run-time customization of @INC can be enabled by passing the
-C<-Dusesitecustomize> flag to Configure. When enabled, this will make perl
-run F<$sitelibexp/sitecustomize.pl> before anything else. This script can
-then be set up to add additional entries to @INC.
-
-=item Relocatable installations
-
-There is now Configure support for creating a relocatable perl tree. If
-you Configure with C<-Duserelocatableinc>, then the paths in @INC (and
-everything else in %Config) can be optionally located via the path of the
-perl executable.
-
-That means that, if the string C<".../"> is found at the start of any
-path, it's substituted with the directory of $^X. So, the relocation can
-be configured on a per-directory basis, although the default with
-C<-Duserelocatableinc> is that everything is relocated. The initial
-install is done to the original configured prefix.
-
-=item strlcat() and strlcpy()
-
-The configuration process now detects whether strlcat() and strlcpy() are
-available. When they are not available, perl's own version is used (from
-Russ Allbery's public domain implementation). Various places in the perl
-interpreter now use them. (Steve Peters)
-
-=item C<d_pseudofork> and C<d_printf_format_null>
-
-A new configuration variable, available as C<$Config{d_pseudofork}> in
-the L<Config> module, has been added, to distinguish real fork() support
-from fake pseudofork used on Windows platforms.
-
-A new configuration variable, C<d_printf_format_null>, has been added,
-to see if printf-like formats are allowed to be NULL.
-
-=item Configure help
-
-C<Configure -h> has been extended with the most commonly used options.
-
-=back
-
-=head2 Compilation improvements
-
-=over 4
-
-=item Parallel build
-
-Parallel makes should work properly now, although there may still be problems
-if C<make test> is instructed to run in parallel.
-
-=item Borland's compilers support
-
-Building with Borland's compilers on Win32 should work more smoothly. In
-particular Steve Hay has worked to side step many warnings emitted by their
-compilers and at least one C compiler internal error.
-
-=item Static build on Windows
-
-Perl extensions on Windows now can be statically built into the Perl DLL.
-
-Also, it's now possible to build a C<perl-static.exe> that doesn't depend
-on the Perl DLL on Win32. See the Win32 makefiles for details.
-(Vadim Konovalov)
-
-=item ppport.h files
-
-All F<ppport.h> files in the XS modules bundled with perl are now
-autogenerated at build time. (Marcus Holland-Moritz)
-
-=item C++ compatibility
-
-Efforts have been made to make perl and the core XS modules compilable
-with various C++ compilers (although the situation is not perfect with
-some of the compilers on some of the platforms tested.)
-
-=item Support for Microsoft 64-bit compiler
-
-Support for building perl with Microsoft's 64-bit compiler has been
-improved. (ActiveState)
-
-=item Visual C++
-
-Perl can now be compiled with Microsoft Visual C++ 2005 (and 2008 Beta 2).
-
-=item Win32 builds
-
-All win32 builds (MS-Win, WinCE) have been merged and cleaned up.
-
-=back
-
-=head2 Installation improvements
-
-=over 4
-
-=item Module auxiliary files
-
-README files and changelogs for CPAN modules bundled with perl are no
-longer installed.
-
-=back
-
-=head2 New Or Improved Platforms
-
-Perl has been reported to work on Symbian OS. See L<perlsymbian> for more
-information.
-
-Many improvements have been made towards making Perl work correctly on
-z/OS.
-
-Perl has been reported to work on DragonFlyBSD and MidnightBSD.
-
-Perl has also been reported to work on NexentaOS
-( http://www.gnusolaris.org/ ).
-
-The VMS port has been improved. See L<perlvms>.
-
-Support for Cray XT4 Catamount/Qk has been added. See
-F<hints/catamount.sh> in the source code distribution for more
-information.
-
-Vendor patches have been merged for RedHat and Gentoo.
-
-DynaLoader::dl_unload_file() now works on Windows.
-
-=head1 Selected Bug Fixes
-
-=over 4
-
-=item strictures in regexp-eval blocks
-
-C<strict> wasn't in effect in regexp-eval blocks (C</(?{...})/>).
-
-=item Calling CORE::require()
-
-CORE::require() and CORE::do() were always parsed as require() and do()
-when they were overridden. This is now fixed.
-
-=item Subscripts of slices
-
-You can now use a non-arrowed form for chained subscripts after a list
-slice, like in:
-
- ({foo => "bar"})[0]{foo}
-
-This used to be a syntax error; a C<< -> >> was required.
-
-=item C<no warnings 'category'> works correctly with -w
-
-Previously when running with warnings enabled globally via C<-w>, selective
-disabling of specific warning categories would actually turn off all warnings.
-This is now fixed; now C<no warnings 'io';> will only turn off warnings in the
-C<io> class. Previously it would erroneously turn off all warnings.
-
-=item threads improvements
-
-Several memory leaks in ithreads were closed. Also, ithreads were made
-less memory-intensive.
-
-C<threads> is now a dual-life module, also available on CPAN. It has been
-expanded in many ways. A kill() method is available for thread signalling.
-One can get thread status, or the list of running or joinable threads.
-
-A new C<< threads->exit() >> method is used to exit from the application
-(this is the default for the main thread) or from the current thread only
-(this is the default for all other threads). On the other hand, the exit()
-built-in now always causes the whole application to terminate. (Jerry
-D. Hedden)
-
-=item chr() and negative values
-
-chr() on a negative value now gives C<\x{FFFD}>, the Unicode replacement
-character, unless when the C<bytes> pragma is in effect, where the low
-eight bits of the value are used.
-
-=item PERL5SHELL and tainting
-
-On Windows, the PERL5SHELL environment variable is now checked for
-taintedness. (Rafael Garcia-Suarez)
-
-=item Using *FILE{IO}
-
-C<stat()> and C<-X> filetests now treat *FILE{IO} filehandles like *FILE
-filehandles. (Steve Peters)
-
-=item Overloading and reblessing
-
-Overloading now works when references are reblessed into another class.
-Internally, this has been implemented by moving the flag for "overloading"
-from the reference to the referent, which logically is where it should
-always have been. (Nicholas Clark)
-
-=item Overloading and UTF-8
-
-A few bugs related to UTF-8 handling with objects that have
-stringification overloaded have been fixed. (Nicholas Clark)
-
-=item eval memory leaks fixed
-
-Traditionally, C<eval 'syntax error'> has leaked badly. Many (but not all)
-of these leaks have now been eliminated or reduced. (Dave Mitchell)
-
-=item Random device on Windows
-
-In previous versions, perl would read the file F</dev/urandom> if it
-existed when seeding its random number generator. That file is unlikely
-to exist on Windows, and if it did would probably not contain appropriate
-data, so perl no longer tries to read it on Windows. (Alex Davies)
-
-=item PERLIO_DEBUG
-
-The C<PERLIO_DEBUG> environment variable no longer has any effect for
-setuid scripts and for scripts run with B<-T>.
-
-Moreover, with a thread-enabled perl, using C<PERLIO_DEBUG> could lead to
-an internal buffer overflow. This has been fixed.
-
-=item PerlIO::scalar and read-only scalars
-
-PerlIO::scalar will now prevent writing to read-only scalars. Moreover,
-seek() is now supported with PerlIO::scalar-based filehandles, the
-underlying string being zero-filled as needed. (Rafael, Jarkko Hietaniemi)
-
-=item study() and UTF-8
-
-study() never worked for UTF-8 strings, but could lead to false results.
-It's now a no-op on UTF-8 data. (Yves Orton)
-
-=item Critical signals
-
-The signals SIGILL, SIGBUS and SIGSEGV are now always delivered in an
-"unsafe" manner (contrary to other signals, that are deferred until the
-perl interpreter reaches a reasonably stable state; see
-L<perlipc/"Deferred Signals (Safe Signals)">). (Rafael)
-
-=item @INC-hook fix
-
-When a module or a file is loaded through an @INC-hook, and when this hook
-has set a filename entry in %INC, __FILE__ is now set for this module
-accordingly to the contents of that %INC entry. (Rafael)
-
-=item C<-t> switch fix
-
-The C<-w> and C<-t> switches can now be used together without messing
-up which categories of warnings are activated. (Rafael)
-
-=item Duping UTF-8 filehandles
-
-Duping a filehandle which has the C<:utf8> PerlIO layer set will now
-properly carry that layer on the duped filehandle. (Rafael)
-
-=item Localisation of hash elements
-
-Localizing a hash element whose key was given as a variable didn't work
-correctly if the variable was changed while the local() was in effect (as
-in C<local $h{$x}; ++$x>). (Bo Lindbergh)
-
-=back
-
-=head1 New or Changed Diagnostics
-
-=over 4
-
-=item Use of uninitialized value
-
-Perl will now try to tell you the name of the variable (if any) that was
-undefined.
-
-=item Deprecated use of my() in false conditional
-
-A new deprecation warning, I<Deprecated use of my() in false conditional>,
-has been added, to warn against the use of the dubious and deprecated
-construct
-
- my $x if 0;
-
-See L<perldiag>. Use C<state> variables instead.
-
-=item !=~ should be !~
-
-A new warning, C<!=~ should be !~>, is emitted to prevent this misspelling
-of the non-matching operator.
-
-=item Newline in left-justified string
-
-The warning I<Newline in left-justified string> has been removed.
-
-=item Too late for "-T" option
-
-The error I<Too late for "-T" option> has been reformulated to be more
-descriptive.
-
-=item "%s" variable %s masks earlier declaration
-
-This warning is now emitted in more consistent cases; in short, when one
-of the declarations involved is a C<my> variable:
-
- my $x; my $x; # warns
- my $x; our $x; # warns
- our $x; my $x; # warns
-
-On the other hand, the following:
-
- our $x; our $x;
-
-now gives a C<"our" variable %s redeclared> warning.
-
-=item readdir()/closedir()/etc. attempted on invalid dirhandle
-
-These new warnings are now emitted when a dirhandle is used but is
-either closed or not really a dirhandle.
-
-=item Opening dirhandle/filehandle %s also as a file/directory
-
-Two deprecation warnings have been added: (Rafael)
-
- Opening dirhandle %s also as a file
- Opening filehandle %s also as a directory
-
-=item Use of -P is deprecated
-
-Perl's command-line switch C<-P> is now deprecated.
-
-=item v-string in use/require is non-portable
-
-Perl will warn you against potential backwards compatibility problems with
-the C<use VERSION> syntax.
-
-=item perl -V
-
-C<perl -V> has several improvements, making it more useable from shell
-scripts to get the value of configuration variables. See L<perlrun> for
-details.
-
-=back
-
-=head1 Changed Internals
-
-In general, the source code of perl has been refactored, tidied up,
-and optimized in many places. Also, memory management and allocation
-has been improved in several points.
-
-When compiling the perl core with gcc, as many gcc warning flags are
-turned on as is possible on the platform. (This quest for cleanliness
-doesn't extend to XS code because we cannot guarantee the tidiness of
-code we didn't write.) Similar strictness flags have been added or
-tightened for various other C compilers.
-
-=head2 Reordering of SVt_* constants
-
-The relative ordering of constants that define the various types of C<SV>
-have changed; in particular, C<SVt_PVGV> has been moved before C<SVt_PVLV>,
-C<SVt_PVAV>, C<SVt_PVHV> and C<SVt_PVCV>. This is unlikely to make any
-difference unless you have code that explicitly makes assumptions about that
-ordering. (The inheritance hierarchy of C<B::*> objects has been changed
-to reflect this.)
-
-=head2 Elimination of SVt_PVBM
-
-Related to this, the internal type C<SVt_PVBM> has been removed. This
-dedicated type of C<SV> was used by the C<index> operator and parts of the
-regexp engine to facilitate fast Boyer-Moore matches. Its use internally has
-been replaced by C<SV>s of type C<SVt_PVGV>.
-
-=head2 New type SVt_BIND
-
-A new type C<SVt_BIND> has been added, in readiness for the project to
-implement Perl 6 on 5. There deliberately is no implementation yet, and
-they cannot yet be created or destroyed.
-
-=head2 Removal of CPP symbols
-
-The C preprocessor symbols C<PERL_PM_APIVERSION> and
-C<PERL_XS_APIVERSION>, which were supposed to give the version number of
-the oldest perl binary-compatible (resp. source-compatible) with the
-present one, were not used, and sometimes had misleading values. They have
-been removed.
-
-=head2 Less space is used by ops
-
-The C<BASEOP> structure now uses less space. The C<op_seq> field has been
-removed and replaced by a single bit bit-field C<op_opt>. C<op_type> is now 9
-bits long. (Consequently, the C<B::OP> class doesn't provide an C<seq>
-method anymore.)
-
-=head2 New parser
-
-perl's parser is now generated by bison (it used to be generated by
-byacc.) As a result, it seems to be a bit more robust.
-
-Also, Dave Mitchell improved the lexer debugging output under C<-DT>.
-
-=head2 Use of C<const>
-
-Andy Lester supplied many improvements to determine which function
-parameters and local variables could actually be declared C<const> to the C
-compiler. Steve Peters provided new C<*_set> macros and reworked the core to
-use these rather than assigning to macros in LVALUE context.
-
-=head2 Mathoms
-
-A new file, F<mathoms.c>, has been added. It contains functions that are
-no longer used in the perl core, but that remain available for binary or
-source compatibility reasons. However, those functions will not be
-compiled in if you add C<-DNO_MATHOMS> in the compiler flags.
-
-=head2 C<AvFLAGS> has been removed
-
-The C<AvFLAGS> macro has been removed.
-
-=head2 C<av_*> changes
-
-The C<av_*()> functions, used to manipulate arrays, no longer accept null
-C<AV*> parameters.
-
-=head2 $^H and %^H
-
-The implementation of the special variables $^H and %^H has changed, to
-allow implementing lexical pragmas in pure Perl.
-
-=head2 B:: modules inheritance changed
-
-The inheritance hierarchy of C<B::> modules has changed; C<B::NV> now
-inherits from C<B::SV> (it used to inherit from C<B::IV>).
-
-=head2 Anonymous hash and array constructors
-
-The anonymous hash and array constructors now take 1 op in the optree
-instead of 3, now that pp_anonhash and pp_anonlist return a reference to
-an hash/array when the op is flagged with OPf_SPECIAL. (Nicholas Clark)
-
-=head1 Known Problems
-
-There's still a remaining problem in the implementation of the lexical
-C<$_>: it doesn't work inside C</(?{...})/> blocks. (See the TODO test in
-F<t/op/mydef.t>.)
-
-Stacked filetest operators won't work when the C<filetest> pragma is in
-effect, because they rely on the stat() buffer C<_> being populated, and
-filetest bypasses stat().
-
-=head2 UTF-8 problems
-
-The handling of Unicode still is unclean in several places, where it's
-dependent on whether a string is internally flagged as UTF-8. This will
-be made more consistent in perl 5.12, but that won't be possible without
-a certain amount of backwards incompatibility.
-
-=head1 Platform Specific Problems
-
-When compiled with g++ and thread support on Linux, it's reported that the
-C<$!> stops working correctly. This is related to the fact that the glibc
-provides two strerror_r(3) implementation, and perl selects the wrong
-one.
-
-=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/rt3/ . There may also be
-information at http://www.perl.org/ , the Perl Home Page.
-
-If you believe you have an unreported bug, please run the B<perlbug>
-program included with your release. Be sure to trim your bug down
-to a tiny but sufficient test case. Your bug report, along with the
-output of C<perl -V>, will be sent off to perlbug@perl.org to be
-analysed by the Perl porting team.
-
-=head1 SEE ALSO
-
-The F<Changes> file and the perl590delta to perl595delta man pages for
-exhaustive details on what changed.
-
-The F<INSTALL> file for how to build Perl.
-
-The F<README> file for general stuff.
-
-The F<Artistic> and F<Copying> files for copyright information.
-
-=cut