If you've not heard of it, MacRuby is an implementation of Ruby 1.9 directly on top of Mac OS X core technologies such as the Objective-C runtime and garbage collector, the LLVM compiler infrastructure and the Foundation and ICU frameworks. Basically means you write in Ruby using Objective-C frameworks, and vice versa. It's pretty damn cool to be honest!

So I just installed ruby 1.9.1 through MacPorts and wanted to easily migrate my rubygems across from 1.8 to see which ones would fail to install.