#!/usr/bin/perl
use strict;
use Tk;
use Tk::ProgressBar;

my $mw=MainWindow->new;

my $percent;

my $pb=$mw->ProgressBar(
   -height      => 0,
   -width       => 20,
   -length      => 100,
   -colors=>[0,'blue'],
   -blocks=>100,
  )->pack;

my $btn=$mw->Button(
   -command => \&show_progress,
   -text    => 'Run program',
  )->pack;
  
MainLoop;

sub show_progress{
    for (1..100) {
        $percent=rand(100);
       $pb->value($percent);
    }
}