$location = $thingy->get_location( $l );

##</code><code>##

$building = $location->get_building( $b );

##</code><code>##

$building = $thingy->get_location( $l )->get_building( $b );

#or

$building = $thingy->get_building_by_location( $l, $b );

##</code><code>##

$cost = $thingy->get_location( $l )->get_building( $b )->cost;
$totals = $location->get_totals;
$upkeep = $building->get_upkeep;

##</code><code>##

foreach my $l ( $thingy->all_locations )
    {
    foreacn my $b ( $b->all_buildings )
        {
        $b->set_cost( $b->cost + 1 );
        }
    }

##</code><code>##

while( my $location = $thingy->next_location )
    {
    ...
    }