#!/usr/bin/perl

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

my %hash = (key1 => {
                     subkey1 => [ qw(a number of elements in an array) ],
                    },
            key2 => "value2");

my %hash2 = %hash;

$hash2{key1}->{subkey1} = [ qw(other elements in an array) ];
print Dumper(\%hash);
print Dumper(\%hash2);