$VAR1 = {
          'k1' => {
                    'k11' => [
                               'v1',
                               'v2'
                             ],
                    'k12' => 'w00t!'
                  },
          'k2' => {
                    'k21' => 'what?',
                    'k22' => []
                  }
        };
$VAR1->{'k2'}{'k22'} = $VAR1->{'k1'}{'k11'};