#!/usr/bin/perl

use warnings; 
use strict;
use Data::Dumper;

BEGIN {
		my %SeenMerged = ();

		sub mergehashes{	 # Dies on circular references
			my @hashrefs = @_;
			die "Passed a non hashref" if grep { ref $_ ne 'HASH' } @hashrefs;
			my %merged = ();

			my @seen = grep { ref $_ eq 'HASH' }  @SeenMerged{@hashrefs}; # Break circular links..

			if (@seen){
				die "contains a circular reference! bailing...";
			}

			@SeenMerged{@hashrefs} = @hashrefs;

			foreach my $h (@hashrefs){
				while (my ($k,$v) = each %$h ){
					push @{$merged{$k}}, $v;
				}
			}

			while (my ($k,$v) = each %merged){
				my @hashes = grep { ref $_ eq 'HASH' } @$v;
				$merged{$k} = $v->[0] if (@$v == 1 && !ref $v->[0]);	
				$merged{$k}  = mergehashes(@hashes) if @hashes;
			}

			delete @SeenMerged{@hashrefs};
			return \%merged;
		}

}

my %hash1 = (
          red => 1,
          brown => {
                    green => 1,
                    blue => {
                             yellow => 1,
                            },
                    black => 1,
                   },
          gray => 1,
         );

my %hash2 = (
          white => 1,
          brown => {
                    purple => 1,
                   },
		  
         );


my $merged = mergehashes(\%hash1, \%hash2) ;#or die "Couldn't merge!";

print Dumper($merged);