You can only take a reference to a subroutine of some sort in perl5 (perl6 will have more sophisticated binding to allow you to pre-populate certain parameters and pass that code ref around instead of the original routine). So here what I'm doing is creating an anonymous sub that is also a closure - it's closed on $self, retaining the current value of $self at the time of this routine. It then calls the routine we want with the parameters we want - even though the Tk code can't know what $self is to pass it in.

As to your assuming lines - I'm not sure, I'm not a Tk user. ;-)