Hi, I'm sorry I don't have an exact answer for you, as my mind is not on Perl these days, but I did see that no one has given you a reply, so here is what I can offer.

You probably need to make a derived menu widget of your own. See Making a derived Tk::Text object for an example of how to do this with a text widget. Also see Deleting Menu Item from Menu for an introduction to the complexity of the Menu widget's arrays.