many businesses simply don't have COBOL around anymore

I strongly disagree. Every large financial or supply-chain client I've worked with has COBOL in place for order entry and/or accounting functions. It's still used heavily for data-intensive "business back-end" systems.

If you qualify what kind of businesses you mean (by line or by size), I may be more inclined to agree, but that's a pretty broad statement you're making.

As for what the questioner originally asked, I don't think any of the choices will make Perl easier to learn, but I do think learning COBOL will teach TIMTOWTDI better than the others.