Unpublished: a shell written in pure Ruby, blurring the line between "shell-land" and "ruby-land" (think xonsh, only it does not "fallback" to the other side of the world at parse time. it's all first class Ruby), and that can also work with mRuby.

Why mRuby? Well this is the first step of a larger dumb project where I'd have pure Ruby as Linux init/userland and boot straight to it (like these old Amstrad or whatever booted straight to BASIC), then maybe even write a toy kernel in Ruby and drop Linux as well.

I have little time to work in it so it's snail pace but I'm getting near the "I can use this shell" minimal featureset (basically basic input, exec, redir, and pipes) line. That's my "fail fast" part, and iteratively implement features as pain shows me that I really need this or that day to day by using it as my default shell.