This is a sample implementation of summing by just state and then also by city and state.

while ( ... )
{
    my $last_name = ...;
    my $address = ...;
    my $city = ...;
    my $state = ...;

    # Aggregate by state
    $SumStates{ $state }++;

    # Aggregate by city
    $SumCityStates{ $state }{ $city }++;
}

# Print sums
for my $state ( keys %SumStates )
{
    print "$state: $SumStates{ $state }\n";

    for my $city ( keys %{ $SumCityStates{ $state } } )
    {
        print "    $city: $SumCityStates{ $state }{ $city }\n";
    }
}
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