foreach my $outerkey (keys %hash_of_hash_of_arrays) {
  print "'$outerkey'";

  foreach my $innerkey (keys %hash_of_hash_of_arrays{$outerkey}) {
    print "\t'$hash_of_hash_of_arrays{$outerkey}{$innerkey}'";

    foreach my $array_item (@{ $hash_of_hash_of_arrays{$outerkey}{$innerkey} })
    {
      print "array item: $array_item";
    }
  }
}