#!/usr/bin/perl
use warnings;
use strict;
use Tk;

my $mw=tkinit;

my @selects;

my $lb1 = $mw->Listbox->pack();
$lb1->insert('end',('A'..'J'));

$lb1->bind('<Enter>' => sub{ $lb1->focus });

$mw->bind('<KeyPress>' => sub  {
           $lb1->focus;
           my $e = $lb1->XEvent;    # get reference to X11 event structure 
           my $key =  $e->K;

# comment out the if {} and see what happens
           if( $key eq 'Return' ){
	            push @selects, $lb1->get('active');
            	    $lb1->itemconfigure('active', -background => 'yellow');
	    }
      
          $mw->update;
          print "@selects\n";
     } );

MainLoop;