#!/usr/bin/perl
use Benchmark;
use strict;

my ( @nums, $x );

for (1..1000) {
    my $r = int(rand(5));
    push @nums, $r > 0 ? $r : undef;
}

timethese(-10, {
    Test_defined => 'for (@nums) { if ( defined $_ and $_ > 2 ) { $x++ }}',
    Do_not_test  => 'for (@nums) { if ( $_ > 2 ) { $x++ }}'
});