perl5120delta — что нового в perl v.5.12.0

perl5120delta - what is new for perl v5.12.0

=encoding utf8

=head1 NAME

perl5120delta - what is new for perl v5.12.0

=head1 DESCRIPTION

This document describes differences between the 5.10.0 release and the
5.12.0 release.

Many of the bug fixes in 5.12.0 are already included in the 5.10.1
maintenance release.

You can see the list of those changes in the 5.10.1 release notes
(L<perl5101delta>).

=head1 Core Enhancements

=head2 New C<package NAME VERSION> syntax

This new syntax allows a module author to set the $VERSION of a namespace
when the namespace is declared with 'package'. It eliminates the need
for C<our $VERSION = ...> and similar constructs. E.g.

package Foo::Bar 1.23;
# $Foo::Bar::VERSION == 1.23

There are several advantages to this:

=over

=item *

C<$VERSION> is parsed in exactly the same way as C<use NAME VERSION>

=item *

C<$VERSION> is set at compile time

=item *

C<$VERSION> is a version object that provides proper overloading of
comparison operators so comparing C<$VERSION> to decimal (1.23) or
dotted-decimal (v1.2.3) version numbers works correctly.

=item *

Eliminates C<$VERSION = ...> and C<eval $VERSION> clutter

=item *

As it requires VERSION to be a numeric literal or v-string
literal, it can be statically parsed by toolchain modules
without C<eval> the way MM-E<gt>parse_version does for C<$VERSION = ...>

=back

It does not break old code with only C<package NAME>, but code that uses
C<package NAME VERSION> will need to be restricted to perl 5.12.0 or newer
This is analogous to the change to C<open> from two-args to three-args.
Users requiring the latest Perl will benefit, and perhaps after several
years, it will become a standard practice.

However, C<package NAME VERSION> requires a new, 'strict' version
number format. See L<"Version number formats"> for details.

=head2 The C<...> operator

A new operator, C<...>, nicknamed the Yada Yada operator, has been added.
It is intended to mark placeholder code that is not yet implemented.
See L<perlop/"Yada Yada Operator">.

=head2 Implicit strictures

Using the C<use VERSION> syntax with a version number greater or equal
to 5.11.0 will lexically enable strictures just like C<use strict>
would do (in addition to enabling features.) The following: