This sounds like a cool idea to me.

To be honest I've been looking for a decent robe-type-item-of-apparel for some time and if I could get one branded in the "craft" of perl, then I'd be jumping the queue to get one!

The logo issue is a tricky one... and I'm sure we'll get a lot of suggestions. Personally I'd definitely go for the

#!/usr/bin/perl -w
use strict;
[download]

on there somewhere - possibly in smallish type on the front upper left (normal logo position).

The back is more difficult, although the line of t-shirts on www.thinkgeek.com offer a variety of ideas.

We want something cool... but clever... just like us brother monks ;-)

Fleece is a nice idea, for those evenings huddled in front of the screen wrestling with the mysteries of some arcane .pm module, coffee in one hand, robe wrapped around you with the other (or is it just me? Thinking back to my freezing-accomadation-student-days).
Might get a bit hot in the Summer though.... How's about a Summer robe and a Winter robe line?

I'd better stop this ramble now... the possibilities are fairly wide... but to the idea -

Definitely.

(Where can I pre-order for Christmas? ;-))