I'm gathering statistics from thousands of pull requests in GitHub. I wrote a little Lisp program to do that. It's taking a long time because it has to make a lot of API calls to GitHub and the calls are rate limited.
After about half an hour, I got an unexpected error. A user who made the pull request I was looking at had deleted their account. No problem. I used the Lisp debugger to walk up the stack to a convenient frame and returned NIL from that frame, causing that particular PR to be skipped. The program continued running from where it left off. I didn't have to restart from the beginning and lose a half hour of work.
The Lisp debugger for the win!
