#!/usr/bin/perl -w
                                                                                
use strict;
use warnings;
                                                                                
use Tk;
use Tk::ProgressBar;
                                                                                
my $percent_done = 0;
                                                                                
my $mw  = new MainWindow(-title => 'Progress Bar Demo');
my $top = $mw->Frame()->pack(-expand => 1, -fill => 'both');
my $pb  = $top->ProgressBar(
            -width    => 20,
            -height   => 200,
            -from     => 0,
            -to       => 100,
            -blocks   => 10,
            -colors   => [0, 'green', 50, 'yellow', 80, 'red'],
            -variable => \$percent_done
          );
$pb->pack();
$mw->after(100 => \&main_loop);
MainLoop;
                                                                                
sub main_loop {
    for (my $i = 0; $i < 100; $i++) {
        $percent_done = $i;
        $mw->update();
        select(undef, undef, undef, 0.1);
    }
}