Per bug RT 98576, PDF::API2 has a construction it calls a "spline", which is a cubic Bezier curve with two synthesized control points. Now, in most cases of splines that I've seen, the curve passes through all the control points, and what PDF::API2 offers may be better termed a "B-spline" or "approximation spline" (I'm not a mathematician, so I can't tell you for sure). I have clarified the spline documentation (POD) to reflect this. Possibly, we may want to offer one or more additional spline types, either as options on spline(), or new methods.
Any suggestions on what would be useful?