#!/usr/bin/perl
use strict;
use warnings;
use Data::Dumper;
use Benchmark::Forking qw( cmpthese );

my %hash = ( "a" => 1,
	     "b" => 2,
	     "c" => 3,
	     "d" => 4
    );

# Export keys from the hash
my @keys = keys %hash;

# Export values from the hash
my @values = values %hash;

my %new_hash_1;
my %new_hash_2;

cmpthese(100000000, {
    'loop indices' => sub {
	for ( 0 .. $#keys ) {
	    $new_hash_1{splice @keys, rand @keys, 1} = splice @values, rand @values, 1;
			    }
    },
	'loop elements' => sub {
	    for ( @keys ) {
		$new_hash_2{splice @keys, rand @keys, 1} = splice @values, rand @values, 1;
	    }
},
	 });

__DATA__

$ perl test.pl
                    Rate  loop indices loop elements
loop indices   5211047/s            --          -58%
loop elements 12531328/s          140%