I have personally seen big companies reject systems because they were written in Perl for this reason.

And it's an extremely valid, if not the most valid, reason to do so. Companies exist to make money. If you want otherwise, go work for a charity. You simply aren't going to make as much (if any) by releasing the source and letting everyone do as they please with it. If you can't understand this basic concept, I recommend you stick to programming and never get into management (heaven, I know ;).