Wouldn't the parameter number be enough to track down any problems?

Well, if instead of passing in a list of constants, he might well be passing in enough arguments, but one of them have a value of undef (which, of course, the second bit of your code would catch).

Seems to me wanting the name of the invalid variable is one more step in princepawn's "the secretary should be able to use the program" ethic. Whether or not we agree with that aim is another matter =)

Philosophy can be made out of anything. Or less -- Jerry A. Fodor