#!/usr/bin/winperl
use strict;
use warnings;

use Tk;
use Tk::ProgressBar;

my $mw = MainWindow->new();

my $prog = $mw->ProgressBar(
  -length => 200,  # Actually width
  -width  => 20,   # Actually height
  -gap    => 0,
  -value  => 0,
  -colors => [0, 'navy'],
)->pack(-pady => 5, -padx => 5),

my @ints = (1 .. 100);
for my $int (@ints) {

  # Set the new value of the progress bar to
  # the old value ($prog->value) plus one.
  $prog->value($prog->value + 1);

  tksleep($mw, 10);

}

# Like sleep, but actually allows the display to be
# updated, and takes milliseconds instead of seconds.
sub tksleep {
  my $mw = shift;
  my $ms = shift;
  my $flag = 0;

  $mw->after($ms, sub { $flag++ });
  $mw->waitVariable(\$flag);
}