I would like to agree. Better but each of those has a pretty high barrier to self-edification and fewer places it will be used in a regular career. Plus, some of what you're talking about in "different concepts" can be handled with different code style in Perl. That's why the Higher Order Perl is so nice, it covers some of that.
I tried to teach myself some Lisp about 3 years ago when I was feeling the same, I'm not progressing feeling, and the resources, tutorials, etc are slim/difficult for a semi-hacker. If I had time now and wasn't resume padding I'd play with something like one of the nascent Parrot driven languages like Amber; or maybe Erlang.