Perl does not have named formal parameters. In practice all you
do is assign to a C<my()> list of these. Variables that aren't
declared to be private are global variables. For gory details
-on creating private variables, see L<"Private Variables via my()">
-and L<"Temporary Values via local()">. To create protected
+on creating private variables, see L</"Private Variables via my()">
+and L</"Temporary Values via local()">. To create protected
environments for a set of functions in a separate package (and
probably a separate file), see L<perlmod/"Packages">.
X<formal parameter> X<parameter, formal>
Like the flattened incoming parameter list, the return list is also
flattened on return. So all you have managed to do here is stored
everything in C<@a> and made C<@b> empty. See
-L<Pass by Reference> for alternatives.
+L</Pass by Reference> for alternatives.
A subroutine may be called using an explicit C<&> prefix. The
C<&> is optional in modern Perl, as are parentheses if the
=head2 Lexical Subroutines
X<my sub> X<state sub> X<our sub> X<subroutine, lexical>
-B<WARNING>: Lexical subroutines are still experimental. The feature may be
-modified or removed in future versions of Perl.
-
-Lexical subroutines are only available under the C<use feature
-'lexical_subs'> pragma, which produces a warning unless the
-"experimental::lexical_subs" warnings category is disabled.
-
Beginning with Perl 5.18, you can declare a private subroutine with C<my>
or C<state>. As with state variables, the C<state> keyword is only
available under C<use feature 'state'> or C<use 5.010> or higher.
+Prior to Perl 5.26, lexical subroutines were deemed experimental and were
+available only under the C<use feature 'lexical_subs'> pragma. They also
+produced a warning unless the "experimental::lexical_subs" warnings
+category was disabled.
+
These subroutines are only visible within the block in which they are
declared, and only after that declaration:
+ # Include these two lines if your code is intended to run under Perl
+ # versions earlier than 5.26.
no warnings "experimental::lexical_subs";
use feature 'lexical_subs';
So, in general, "state" subroutines are faster. But "my" subs are
necessary if you want to create closures:
- no warnings "experimental::lexical_subs";
- use feature 'lexical_subs';
-
sub whatever {
my $x = shift;
my sub inner {
The two main uses for this are to switch back to using the package sub
inside an inner scope:
- no warnings "experimental::lexical_subs";
- use feature 'lexical_subs';
-
sub foo { ... }
sub bar {
package MySneakyModule;
- no warnings "experimental::lexical_subs";
- use feature 'lexical_subs';
-
our sub do_something { ... }
sub do_something_with_caller {
returning a list:
func(@foo);
- func( split /:/ );
+ func( $text =~ /\w+/g );
Then you've just supplied an automatic C<scalar> in front of their
argument, which can be more than a bit surprising. The old C<@foo>
which used to hold one thing doesn't get passed in. Instead,
C<func()> now gets passed in a C<1>; that is, the number of elements
-in C<@foo>. And the C<split> gets called in scalar context so it
-starts scribbling on your C<@_> parameter list. Ouch!
+in C<@foo>. And the C<m//g> gets called in scalar context so instead of a
+list of words it returns a boolean result and advances C<pos($text)>. Ouch!
If a sub has both a PROTO and a BLOCK, the prototype is not applied
until after the BLOCK is completely defined. This means that a recursive
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