I may be missing what you're trying to do here, so ignore me if I'm wrong.

The Tk documentation habitually uses ?option? to indicate optional stuff in commands. You don't need (or want) the question marks in your code. This is a bit of a problem due to a lot of the Perl/Tk docs being copied across from Tcl/Tk, some bits don't follow Perl doc conventions.

Hope this helps,
Kev

Kevin O'Rourke