widget is a program which is included in every Tk install. As cited above, if you are running Activestate Perl, you will find it as widget.bat in your perl\bin directory. *NIX users will find it in /usr/bin or suchlike -- wherever perl is to be found.

FYI, however, here is a working ProgressBar example:

#!/usr/bin/perl -w
use strict;
use Tk;
use Tk::ProgressBar;
use vars qw($status_var);

my $main = Tk::MainWindow->new;
$main->title('Foo');
$main->Label(-text=>'Loading, please wait...')->pack;
$status_var = 0;

$main->ProgressBar(
                   -variable => \$status_var,
                   -from => 0,
                   -to => 100
                  )->pack;
$main->after(500,\&do_stuff);
Tk::MainLoop;

sub do_stuff {
  for (1..10) {
    $status_var+= 10;
    $main->update;
    sleep 1;
  }
  Tk::exit;
}
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perl -e 'print "I love $^X$\"$]!$/"#$&V"+@( NO CARRIER'