Tk::waitVariableX - AUTOLOAD failed

[jowe]

Hi PerlMonks,
the following code snippet demonstates my problem:

#!/usr/bin/perl
use strict;
use warnings;
use Tk;
use Tk::waitVariableX;
my $mw = MainWindow->new();
my $unchanged_var = ' ';
while ()
{
    my $numtime = time ();
    my ($curr_sec, $curr_min, $curr_hour, $curr_mday, $curr_month, $cu
+rr_year, $curr_wday, $curr_yday, $curr_isdst) = localtime ($numtime);
+   
    my $lab1 = $mw->Label (-text => 'time returned: ' . $curr_hour . '
+:' . $curr_min . ':' . $curr_sec)
                        ->form(-left => '%5', -top => '%10');    
    $lab1->update;    
    $mw->waitVariableX (5 * 1000, \$unchanged_var);    # sleep 5 secon
+ds
}                                               
MainLoop;

The package (Tk::waitVariableX from cpan) installs ok but it seems like something is not set during the install process.
My environment: Windows 7, ActivePerl 5.16.3.1603 MSWin32, Tk: 804.030, Tk::waitVariableX: 1.0
The same behavior under Linux.
Could you please let me know what I am doing wrong.
Thanks for your help - jowe