I think this is not a general shell like bash or csh, more of a custom REPL for some specific set of commands. A critical feature of every other shell is how they handle pipes, and this one doesn't seem to have gotten that far yet.

Perhaps it would have been better to wrap the limited shell functionalities in in gem instead, and run that inside `irb`. Currently the majority of the lines appears to be reimplementing a REPL, but those would come for free with `irb`.