use strict;
use warnings;

use Benchmark qw( timethese cmpthese );
my $results = timethese(
    5000,
    {   orig => sub {
            delete $P::x{some_key};
            for ( 1 .. 1000 ) {
                $P::x{some_key} ||= ( f(), 1 );
            }
        },
        alt_1 => sub {
            delete $P::x{some_key};
            for ( 1 .. 1000 ) {
                $P::x{some_key} = $P::x{some_key} || ( f(), 1 );
            }
        },
        alt_2 => sub {
            delete $P::x{some_key};
            for ( 1 .. 1000 ) {
                if ( not $P::x{some_key} ) {
                    $P::x{some_key} = 1;
                    f();
                }
            }
        },
    }
);
cmpthese($results);

sub f() {
    #No op.
}