use warnings;
use strict;
use feature 'say';

my $h = {a=>1, b=>2, c=>3, d=>4};

for my $k1 (keys %$h) {
	my $v1 = $h->{$k1};
	say "external $k1 => $v1";
	while ( my ($k2, $v2) = each %$h ) {
		say "  internal $k2 => $v2";
	}
}