If you already know Perl, then learning the Tk bit won't take you long.

Checkout the Image Supplement to the Perl/Tk FAQ for a quick overview.

Look at the Perl/Tk Chatterbox Client (real life code is good!).
If you need help on syntax, checkout the Tk Documentation.
Another good source of information - the comp.lang.perl.tk FAQs.

Look at Win32::Process documentation on CPAN for how to start the dos based program.
You'll want to checkout Hiding the DOS window on Win32 too.

- dystrophy -