#!/usr/bin/perl
use strict;
use Data::Dumper;

my %europe = (
        skin => "euro-white",
        language => {
                default => "euro-englisch",
                instrument => "euro-clarinet",
        },
        politics => "euro-democratic",
);
my %german = (
        skin => "de-white",
        language => {
                default => "de-german"
        }
);
my %bavarian = (
        skin => "bav-white",
        language => {
                default => "bav-bavarian"
        }
);

# this is not enough, german/language overwrites
# the complete hash of euro/language
my %woman = %europe;

deepmerge(\%woman, \%german);
deepmerge(\%woman, \%bavarian);

print Dumper(\%woman);
# result is this:
# $VAR1 = {
#           'skin' => 'bav-white',
#           'politics' => 'euro-democratic',
#           'language' => {
#                           'default' => 'bav-bavarian'
# ** this is not here: instrument => "euro-clarinet",
#                         }
#         };
unless ($woman{language}->{instrument}) {
        die "Error: Language instrument is not there";
} else {
        print "It worked\n";
}

sub deepmerge {
    my ($into, $this) = @_;
    
    for my $k (keys %$this) {
        if (defined $k and 
            exists $into->{$k} and 
            defined $into->{$k} and 
            ref($into->{$k}) eq 'HASH' and
            ref($this->{$k}) eq 'HASH') {
        
            deepmerge($into->{$k}, $this->{$k});
        
        } elsif (defined $k) {
            $into->{$k} = $this->{$k};
        }
    }
}