#!/usr/bin/perl -w
use strict;
use Benchmark qw( timethese );

use vars qw( %hash );
@hash{ 'A' .. 'Z', 'a' .. 'z' } = (1) x 52; 

timethese 100000, {
        'defined' => sub {
                if (defined $hash{X}) { };
        },
        'exists' => sub {
                if (exists $hash{X}) { };
        },
        'as is' => sub {
                if ($hash{X}) { };
        },
};