use Tk;
use Tk::ProgressBar;

my $percent_done = 0;
my $i = 0;

our $mw = MainWindow->new(-title => 'ProgressBar example');

my $progress = $mw->ProgressBar( -variable => \$percent_done )->pack(-fill => 'x');

$mw->Button(-text => 'Go!', -command=> sub {
   for ($i = 0; $i < 1000; $i++) { 
     $percent_done = $i/10;
     $mw->update;  # otherwise we don't see how far we are.
  }
 })->pack(-side => 'bottom');

$mw->Button(-text => 'Exit!', -command=> sub {$mw->destroy;}
           )->pack(-side => 'bottom');

MainLoop;