Just for your information:

   printf "After deleting: state=%s zip= %s\n",
      $location_hash->{ $city }->{ 'ST' },
      $location_hash->{ $city }->{ 'ZIP' };
[download]

This code will re-create the key $city} in %$location_hash. $location_hash->{$city} has to exists before it can look up ST and/or ZIP. (autovivication)

Another note: $location_hash->{$city}->{'ST'} is the same as: $location_hash->{$city}{'ST'} which is the same as: <code>$location_hash->{$city}{ST}