That’s not a great thing to have to say, is it? However, I bet you’ve said it before and may not have immediately know why.
With liberal use of puts and maybe pry, you can figure out what a problem might be next time you run it, but sometimes you need to figure out what that problem is right now.
As it turns out, and I know this is a shocker, Ruby processes are just regular processes. They can be debugged with gdb.
Having recently had the need to find out why a job of mine was running particularly slowly, I found out about this lovely tool the hard way: frantic googling. I found some very useful functions for gdb in a blog post by Rasmus on Ruby callstacks.