package feature;
-our $VERSION = '1.27';
+our $VERSION = '1.39';
our %feature = (
fc => 'feature_fc',
state => 'feature_state',
switch => 'feature_switch',
evalbytes => 'feature_evalbytes',
+ postderef => 'feature_postderef',
array_base => 'feature_arybase',
+ signatures => 'feature_signatures',
current_sub => 'feature___SUB__',
+ refaliasing => 'feature_refaliasing',
+ lexical_subs => 'feature_lexsubs',
+ postderef_qq => 'feature_postderef_qq',
unicode_eval => 'feature_unieval',
unicode_strings => 'feature_unicode',
);
"5.10" => [qw(array_base say state switch)],
"5.11" => [qw(array_base say state switch unicode_strings)],
"5.15" => [qw(current_sub evalbytes fc say state switch unicode_eval unicode_strings)],
- "all" => [qw(array_base current_sub evalbytes fc say state switch unicode_eval unicode_strings)],
+ "all" => [qw(array_base current_sub evalbytes fc lexical_subs postderef postderef_qq refaliasing say signatures state switch unicode_eval unicode_strings)],
"default" => [qw(array_base)],
);
$feature_bundle{"5.13"} = $feature_bundle{"5.11"};
$feature_bundle{"5.14"} = $feature_bundle{"5.11"};
$feature_bundle{"5.16"} = $feature_bundle{"5.15"};
+$feature_bundle{"5.17"} = $feature_bundle{"5.15"};
+$feature_bundle{"5.18"} = $feature_bundle{"5.15"};
+$feature_bundle{"5.19"} = $feature_bundle{"5.15"};
+$feature_bundle{"5.20"} = $feature_bundle{"5.15"};
+$feature_bundle{"5.21"} = $feature_bundle{"5.15"};
+$feature_bundle{"5.22"} = $feature_bundle{"5.15"};
$feature_bundle{"5.9.5"} = $feature_bundle{"5.10"};
our $hint_shift = 26;
=head2 Lexical effect
Like other pragmas (C<use strict>, for example), features have a lexical
-effect. C<use feature qw(foo)> will only make the feature "foo" available
+effect. C<use feature qw(foo)> will only make the feature "foo" available
from that point to the end of the enclosing block.
{
=head2 The 'switch' feature
+B<WARNING>: Because the L<smartmatch operator|perlop/"Smartmatch Operator"> is
+experimental, Perl will warn when you use this feature, unless you have
+explicitly disabled the warning:
+
+ no warnings "experimental::smartmatch";
+
C<use feature 'switch'> tells the compiler to enable the Perl 6
given/when construct.
=head2 The 'unicode_strings' feature
-C<use feature 'unicode_strings'> tells the compiler to use Unicode semantics
+C<use feature 'unicode_strings'> tells the compiler to use Unicode rules
in all string operations executed within its scope (unless they are also
within the scope of either C<use locale> or C<use bytes>). The same applies
to all regular expressions compiled within the scope, even if executed outside
-it.
+it. It does not change the internal representation of strings, but only how
+they are interpreted.
C<no feature 'unicode_strings'> tells the compiler to use the traditional
-Perl semantics wherein the native character set semantics is used unless it is
+Perl rules wherein the native character set rules is used unless it is
clear to Perl that Unicode is desired. This can lead to some surprises
when the behavior suddenly changes. (See
L<perlunicode/The "Unicode Bug"> for details.) For this reason, if you are
This feature is available from Perl 5.16 onwards.
+=head2 The 'lexical_subs' feature
+
+B<WARNING>: This feature is still experimental and the implementation may
+change in future versions of Perl. For this reason, Perl will
+warn when you use the feature, unless you have explicitly disabled the
+warning:
+
+ no warnings "experimental::lexical_subs";
+
+This enables declaration of subroutines via C<my sub foo>, C<state sub foo>
+and C<our sub foo> syntax. See L<perlsub/Lexical Subroutines> for details.
+
+This feature is available from Perl 5.18 onwards.
+
+=head2 The 'postderef' and 'postderef_qq' features
+
+B<WARNING>: This feature is still experimental and the implementation may
+change in future versions of Perl. For this reason, Perl will
+warn when you use the feature, unless you have explicitly disabled the
+warning:
+
+ no warnings "experimental::postderef";
+
+The 'postderef' feature allows the use of L<postfix dereference
+syntax|perlref/Postfix Dereference Syntax>. For example, it will make the
+following two statements equivalent:
+
+ my @x = @{ $h->{a} };
+ my @x = $h->{a}->@*;
+
+The 'postderef_qq' feature extends this, for array and scalar dereference, to
+working inside of double-quotish interpolations.
+
+This feature is available from Perl 5.20 onwards.
+
+=head2 The 'signatures' feature
+
+B<WARNING>: This feature is still experimental and the implementation may
+change in future versions of Perl. For this reason, Perl will
+warn when you use the feature, unless you have explicitly disabled the
+warning:
+
+ no warnings "experimental::signatures";
+
+This enables unpacking of subroutine arguments into lexical variables
+by syntax such as
+
+ sub foo ($left, $right) {
+ return $left + $right;
+ }
+
+See L<perlsub/Signatures> for details.
+
+This feature is available from Perl 5.20 onwards.
+
+=head2 The 'refaliasing' feature
+
+B<WARNING>: This feature is still experimental and the implementation may
+change in future versions of Perl. For this reason, Perl will
+warn when you use the feature, unless you have explicitly disabled the
+warning:
+
+ no warnings "experimental::refaliasing";
+
+This enables aliasing via assignment to references:
+
+ \$a = \$b; # $a and $b now point to the same scalar
+ \@a = \@b; # to the same array
+ \%a = \%b;
+ \&a = \&b;
+ foreach \%hash (@array_of_hash_refs) {
+ ...
+ }
+
+See L<perlref/Assigning to References> for details.
+
+This feature is available from Perl 5.22 onwards.
+
=head1 FEATURE BUNDLES
It's possible to load multiple features together, using
:5.16 say state switch unicode_strings
unicode_eval evalbytes current_sub fc
+ :5.18 say state switch unicode_strings
+ unicode_eval evalbytes current_sub fc
+
+ :5.20 say state switch unicode_strings
+ unicode_eval evalbytes current_sub fc
+
+ :5.22 say state switch unicode_strings
+ unicode_eval evalbytes current_sub fc
+
The C<:default> bundle represents the feature set that is enabled before
any C<use feature> or C<no feature> declaration.
https://perl5.git.perl.org / perl5.git / blobdiff