You can't get there from here

Trading

        sub total {
          my ($sizes, $values, @items) = @_;
          my $total_size = 0;
          my $total_value = 0;

          for my $item (@items) {
            $total_size  += $sizes->{$item};
            $total_value += $values->{$item};
          }
          return ($total_size, $total_value);
        }