c:\>test.pl
eval $hash{'string1'}{'string2'}{'string3'}{'string4'}++
eval $hash{'string3'}{'string4'}++
eval $hash{'string1'}{'string2'}{'string3'}++
$VAR1 = {
          'string3' => {
                         'string4' => 1
                       },
          'string1' => {
                         'string2' => {
                                        'string3' => 5393161
                                      }
                       }
        };