$cost = $h->{Locations}{$location}{Buildings}{$b}{cost};

##</code><code>##

  $cost = $h->Locations->$location->Buildings->$b->cost;

##</code><code>##

  $cost = $h->{"Locations.$location.Buildings.$b.cost"};

##</code><code>##

  while (my ($key, $value) = $h->each)
  {
    print "$key => $value\n";
  }

OUTPUT:

  Locations.Earth.Buildings.PowerPlant.cost => 7
  Locations.Earth.Buildings.PowerPlant.size => 4
  Locations.Earth.Coordinates => 12.0,72.4
  Locations.Squaffle.Buildings.SaltRefinery.cost => 2
  .
  .
  .