|Pathologically Eclectic Rubbish Lister|
> It would be interesting to have an example dataset to compare the performance of any forthcoming pure-perl solution with what postgres indexing can do. Or graphic libraries (like you mentioned earlier).
I'm trying not to cross that road. ;)
If you want you can compare it against a trivial bounding-box approach of spatial indexing.
You add 4 indexed columns for each polygon and use the formula from my first post to eliminate candidates°.
A simplistic pure Perl solution would probably imply sorted arrays, slices and hash intersections for the AND clause.
(Doesn't scale well but can handle 10000 polygons easily)
You already created your test sample, I doubt the OP ever will.
°) Nota bene: this doesn't calculate overlaps, it's just a poor man's spatial index to eliminate impossible combinations.