So it turns out that currently ruby-debug [the *great* debugger for 1.8.x] isn’t quite compatible with 1.9
Are we lost?
Some things you could try
1) run it with ruby’s normal debugger -rdebug  kind of slow
2) run it with unroller gem [kind of stinks, way slow]
3) use a lot of print statements 🙂 fast, kind of less introspection possible 🙂
4) drop to an irb prompt and run some code from there.
you could list the code by creating your own “drop to irb prompt” that listed the code around itself [use caller to discover where you where] then drop to a normal irb prompt.
5) maybe jruby in 1.9 compat mode has a debugger?