pseudo-snippet --
use Tk;
$mw = MainWindow->new;
$tw = $mw->Scrolled ("Text");
$bu = $mw->Button(-text=>"Go",
                  -command=>\&dosomething);
Mainloop;

exit;

sub dosomething {
  for my $i (1 .. 500) {
    $tw->insert('end',"\$i is " . $i);
    };
  }

__END__