#!/usr/bin/perl
use strict;
use warnings FATAL => 'all';

use v5.10;                      # activate say feature

my $h1 = {'a'=>1, 'b'=>2, 'c'=>3, 'd'=>4,};
my $h2 = {'v'=>6, 'x'=>7, 'y'=>8, 'z'=>9,};

while( my ($k1, $v1) = each(%$h1))
{
    say "external $k1 => $v1";
    while( my ($k2, $v2) = each(%$h2))
    {
        say "internal $k2 => $v2";
    }

    # getchar to pause iteration after inner loop
    print "getchar to pause iteration after inner loop\n";
    my $c = <>;
}