I'm taking down this post. I just posted this as a side comment to explain a sentence on my latest blog post. This wasn't meant to be #1 on HN to start a huge war on functional programming... The thoughts are not well formed enough to have a huge audience. Sorry for all the people reading this. And please, don't dig through the history...
This installs a patched ruby 1.9.3-p327 with various performance improvements and a backported COW-friendly GC, all courtesy of funny-falcon.
You will also need a C Compiler. If you're on Linux, you probably already have one or know how to install one. On OS X, you should install XCode, and brew install autoconf
using homebrew.