Update: okay, judging by the responses, most things go. So I’ll make a few recommendations that haven’t come up yet:

For something close to Perl, I definitely recommend Mastering Regular Expressions – no matter how good you think you are with them, if you haven’t had formal education on state machines and regular expressions, you don’t actually know what you’re doing until you’ve read this book.

Something else you absolutely need is an algorithms textbook. I have Algorithms by Sedgewick. If you want to have a hope to ever write computation-heavy code that performs well with large and/or many datasets (what’s nebulously called “scaling”), you need to know your algorithms. Also, even seemingly simple algorithms and data structures can have subtle tradeoffs; choosing correctly can allow you to simplify even already simple code. I’ve heard good things about The Algorithm Design Manual, but not yet read it.

Beyond that, I suggest books on other programming languages – any other programming languages. It’s a cliché by now, but you should really never stop learning. (I have, lately, and I can clearly see how it has stunted my growth. Don’t do it.)