updating label using thread

[stiffyamit]

use Thread;
use warnings;
use Tk;
my $x=10;
my $mw=new MainWindow;
$mw->Label(-text=>"honeywell")->place(-x=>$x,-y=>50);
my $thr = new Thread \&sub1;
sub sub1 { 
  for($i=0;$i<20;$i++){
      $x+=20;
      sleep(2);			
      $mw->update;
	}
}
	MainLoop;

I am trying to update the label so that the text appears going down.I want to implement it using thread.But the text os not sliding down.Can anyone plz help me?