I'm simultaneously amazed and horrified (by the strange but amazing love child you've created between bash and ruby). I spent years (nearly a decade) trying to blend ruby and bash to make the perfect shell, and after never being quite satisfied, I eventually gave up and embraced bash. This does get closer/further than I ever could, and is a fascinating project. I'm going to give it a spin, though I can already imagine the biggest obstacle I'll hit: rubish not being available in the remote environments I need it to, meaning I'll either have to install it (and it's not lightweight currently), or I'll have to live in two different worlds, which isn't usually sustainable.

Kudos though, and great work! I can tell you put a lot of thought and effort into it.