he issue I have is that when no item is selected, I still display stale information for the last item selected.

so call the function yourself? or generate an event

See Tk trigger event, eventGenerate

See Tk::event

See http://search.cpan.org/grep?cpanid=SREZIC&release=Tk-804.030&string=eventgenerate&i=1&n=1&C=0

See http://search.cpan.org/dist/Tk/MANIFEST http://search.cpan.org/src/SREZIC/Tk-804.030/Tixish/examples/perl-tix-tree