G'day DcmbrAgnt,

"... display status on its execution."

I'm having some problems envisaging what you want to do here. If it's a simple action, then some form or status bar might be appropriate. Perhaps it's a long-running action and you want a progress bar. If there are multiple messages that you want to keep, maybe report those in their own widget.

"Could it all be done inside the same Perl script as the program, ..."

You can use Tk::Toplevel in your Tk script. You can customise this however you want.

"I've read that Tk::Derived ... but I've never done that before."

I wrote some information on that just a few weeks ago: "Re: Writing my first PERL/Tk megawidgit".