I knew that GD.pm was a front-end for the C-based GD lib but (a) didn't know where the documentation for Boutell's GD lib was and (b) wouldn't know how to read the C source code for it if I could find it*.

GrummerX++ - thanks for confirming my suspicions about void context!!!

..Guv

* Slight exaggeration; though I wouldn't have a hope of writing C code I am pretty sure I would be able to read it at a beginner level i.e. enough to tell that the function call is in void context :)