You can pass triangle a set of polygons and get back a bunch of triangles that correspond to a single shape. For example, you can make a very good polygon merge program by starting with Triangle. It handles holes, non-convex shapes, and other problems without difficulty.

You'll have to look at Triangle to see what all it does. It is a large topic. I use it to find messed up geometries in large collections of polygons. For example, my code detects self-intersecting polygons (that is, 'bow ties'). There are about a half-dozen such checks that I do on each polygon. The polygons can have hundreds of points or more. My code typically runs one polygon at a time over a collection of about 60,000 polygons. My perl code creates Triangle input files, calls Triangle from backticks, and then processes the Triangle output file. The Graph module is handy for loading the Triangle output data.