I've collected references to error handling but - I have to shamefully admit - have never encountered Common Lisp's condition system.

I'll take the time to read up on it properly, but from a quick glance it seems to me to be in the category of non-local transfer of control with a co-routine flavour.

It looks powerful, but I get the sense that a lot of language designers are on purpose trying to restrict the powers of error handling. So returning sym types or error codes are simpler than throwing exceptions which - again looks to me - to be simpler than allowing transfer of control to be decided at run time as in the condition system.

Again, very interesting. And thank you for making me aware of its existence.