$VAR1 = {
          'foo' => {
                     'bar' => {
                                'baz' => {
                                           'x' => {
                                                    'y' => {
                                                             'z' => {
                                                                      't' => 42
                                                                    }
                                                           }
                                                  }
                                         }
                              }
                   }
        };
          Rate   while  exists foreach
while   21.3/s      --    -10%    -21%
exists  23.6/s     11%      --    -12%
foreach 27.0/s     27%     14%      --