If you are just looking for the symbols to reference the keys, they are (at least in my world):

KP_Up
KP_Down
KP_Left
KP_Right

If, on the other hand, you want to be able to find the key symbols yourself, you can use this code (originally from Mastering Perl/Tk Chapter 15):

#!/usr/bin/perl -w

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";
}
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If I completely misunderstood the question, feel free to elaborate for a better response.

Vavoom