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

my $mw = MainWindow->new;
my $tw = $mw->Scrolled ("Text")->pack;

my $bu = $mw->Button(-text=>"Go",
         -command=>\&dosomething)->pack;

MainLoop;

exit;

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

__END__