#!/usr/bin/perl
use warnings;
use strict;
use Benchmark qw{ cmpthese };

my %h;
@h{1001 .. 2000} = (1) x 1000;
my ($e, $v) = (0) x 2;

cmpthese(-1, {
	exist => sub { for (0..999_999) {   ++$e if exists $h{1001}   } },
	value => sub { for (0..999_999) {   ++$v if $h{1001}          } },
});

__DATA__
        Rate value exist
value 18.3/s    --   -5%
exist 19.3/s    5%    --