use strict;
use Tk;

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";
}