in reply to Is a point in a polygon?
First of all, I think that the question is nice but there's something missing: some code. People will help you kindly with any perl-related question there, but they will not do the homework for you, of course! ;).
Just try to update your question and put your code as clean as possible. Perhaps people will be able to help you (it looks more like an algorithm problem). Just for some help, check which kind of iterative structure fits you more.
Looking by google you will find things like this: algorithm polygon -> Determining Whether A Point Is Inside A Complex Polygon
Hope it helps!