#!/usr/bin/perl --
use strict;
use warnings;
use Tk;
use Tk::Trace;
my $mw = tkinit;
my $tv = "yo";
my $tt = $mw->Entry( )->pack;
$tt->configure( -textvariable , \$tv );
$mw->traceVariable( \$tv, 'w' => [ sub { warn "you changed it @_  "; $_[1]; } ] );
$mw->after( 1000 => sub { $tv.= ' '.rand.' '; } );
$mw->MainLoop;