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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">.

=item Optional pre-match and post-match captures with the /p flag

There is a new flag C</p> for regular expressions.  Using this
makes the engine preserve a copy of the part of the matched string before
the matching substring to the new special variable C<${^PREMATCH}>, the
part after the matching substring to C<${^POSTMATCH}>, and the matched
substring itself to C<${^MATCH}>.

Perl is still able to store these substrings to the special variables
C<$`>, C<$'>, C<$&>, but using these variables anywhere in the program
adds a penalty to all regular expression matches, whereas if you use
the C</p> flag and the new special variables instead, you pay only for
the regular expressions where the flag is used.

For more detail on the new variables, see L<perlvar>; for the use of
the regular expression flag, see L<perlop> and L<perlre>.

=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 inaccessible 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