Well, it won't get rid of at least one argument.
Hmm, say you have routine that draws a single line between p1 and p2. The third "argument", if supplied, could be the layer to place the line on (I know, silly example). It should behave like (drawLine pt1 pt2 [layer]) but optional args not being an option, it could look like (drawLine args), where args is a list, either '(pt1 pt2) or '(pt1 pt2 layer).