my %feature = (
    switch => 'feature_switch',
    say    => "feature_say",
    state  => "feature_state",
);

##</code><code>##

Feature "~~" is not supported by Perl 5.10.0 at ...

##</code><code>##

use feature qw / say /;
@a = (1, 17, 4);
say "first match succeeds" if (@a ~~ 17);
say "second match fails" unless ((1, 17, 4) ~~ 17);

##</code><code>##

first match succeeds
second match fails