#! perl -slw
use strict;
use Benchmark qw[ cmpthese ];

our %hash = 'aaaaa' .. 'dzzzz';

cmpthese 1, {
    a => q[
        my @keys = keys %hash;
        my @vals = values %hash;
        my $x;
        $x = "$keys[ $_ ] :: $vals[ $_ ]" for 0 .. $#keys;
    ],
    b => q[
        my( $k, $v, $x );
        $x = "$k :: $v" while ( $k, $v ) = each %hash;
    ]
};

__END__
  s/iter    a    b
a   3.06   -- -41%
b   1.79  70%   --