[ahefner]

There's still a few Common Lisp features the mainstream would benefit from ripping off. Relevant here is the condition system. Conditions and restarts are still foreign enough that it's hard to explain to people why the "debugger" was a fundamental part of the lisp machine UI, and how much sense that made, and harder still to fathom how you'd adapt that to Unix, where it would morph into some kind of weird IPC tied into the command shell.

It's not just about being able to stop your program and hot-patch code to recover from errors - this should be trivial in any dynamic language. Rather, it's about being able to composably control how to recover from exception conditions (or, really, any branching behavior) both interactively and programmatically in a unified framework.