sub check_price_paid { 
        my $price_paid = param("some_param");
       my $price_to_pay = &calculate_price;
        return $price_to_pay <= $price_paid; # This is where we get problems!!
}

sub calculate_price {
        my $price = &calculate_base_price;
        $price += &calculate_tax($price);
        return $price;
}
 
sub calculate_base_price { 
        my $price = 0;
        foreach (@item) {
                $price += $_ -> price;
        }
        return $price; # this will always be to 2 sig figs.
}
 
sub calculate_tax { 
        my $price = shift;
        my $tax;
 
        $tax = $price * $CONFIGS->{tax} / 100;
        # need to be accounting correct
        $tax *= 10 ** $currency_decimal_places;
        if ($tax =~ /\.(\d)/ && $1 >= 5) { $tax ++} # a cheat, but simple. This rounds up or down, in accounting-correct manner.
        $tax = int $tax;
        $tax /= 10 ** $currency_decimal_places;
 
        return $tax;
}