There is something wrong in your installation. I dunno what, but I've used Tk with ActiveState 5.6, 5.8 and 5.10.

I recommend to start over and USE THE ActiveState installer, their ppm (Perl Package Manager) program to get Tk. If a module is available on the ActiveState site, using their installation program is the easiest way to go. I tested this code on my machine and it works fine.

#!/usr/bin/perl -w
use strict;

use Tk;
my $mwin = MainWindow->new();
$mwin->title("Hello");
MainLoop();  ###oh, this is important to start
             ###the GUI!!!!!
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