Run this program, observe how it works, then bind the correct key symbol into your messagebox code.

#!/usr/bin/perl
use Tk;
$mw = MainWindow->new;

$mw->bind("<Key>", [  sub { print "Key Press: $_[1] \n" } , Ev('K')  ]
+ );

$mw->bind("<KeyRelease>", [ sub { print "Key Release: $_[1] \n" } , Ev
+('K')  ] );

MainLoop;
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