#!/usr/bin/perl
use Benchmark qw(:all :hireswallclock);
$count = 1000;
for(1..$count){
	$hash{$_} = $_;
}
timethese($count, {
	'each' => sub {
		while (my ($key, $value) = each %hash) {
			$hash{$key} = 1; 
		}
	},
	'foreach keys' => sub {
		foreach (keys %hash) {
			$hash{$_} = 1; 
		}
	},
	'for keys' => sub {
		for (keys %hash) {
			$hash{$_} = 1; 
		}
	},
} );