#!/usr/bin/perl

use strict;
use warnings;

sub hash_update
{
    my ($x, $y) = @_;
    
    my $tx = ref $x;
    my $ty = ref $y;
    my $retval;
   
    die "Can not update due to different object type! ($tx != $ty)" unless $tx eq $ty;
   
    if($tx eq "ARRAY")
    {
        $retval = [];
        for my $i (0 .. _min(scalar(@{$x}), scalar(@{$y}))-1)
        {
            die "Array element was not expected!" unless ref $x->[$i];
            push @{$retval}, hash_update($x->[$i], $y->[$i]);
        }       ; 
    }
    elsif($tx eq "HASH")
    {
        $retval = {};
        for my $k (keys %{$x})
        {
            $retval->{$k} = exists $y->{$k} ? hash_update($y->{$k}, $x->{$k}) : $x;
        }
    }
    elsif($x ne "SCALAR")
    {
        $retval = $x;
    }

    return $retval;
}

sub _min
{
    return $_[0] < $_[1] ? $_[0] : $_[1]; 
}