#!/usr/bin/perl
use warnings;
use strict;
use Tk;
#mouse must be positioned over "Exit" button for this to work. 

my $mw = MainWindow->new;
$mw->bind( '<KeyPress>' => \&print_keysym );
$mw->Button(
    -text    => 'Exit',
    -command => sub { exit(); }
)->pack;
MainLoop;

sub print_keysym {
    my $widget = shift;
    my $e      = $widget->XEvent;
    my ( $keysym_text, $keysym_decimal ) = ( $e->K, $e->N );
    print "keysym=$keysym_text, numberic=$keysym_decimal\n";
}