You'd need to keep track of what key was pressed. I'm not a Tk user, so I don't know how to go about doing that offhand.
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Jeff japhy Pinyan,
P.L., P.M., P.O.D, X.S.:
Perl,
regex,
and perlhacker How can we ever be the sold short or the cheated, we who for every service have long ago been overpaid? ~~ Meister Eckhart