Install Ruby 2.0 Preview 2

Ruby 2.0 is still a work in progress, but it's already at preview 2. If you're looking to play with it, here are some steps to install Ruby 2.0 Preview 2 on Mac OSX Mountain Lion (and older OSX versions)

Install Homebrew:

ruby -e "$(curl -fsSkL raw.github.com/mxcl/homebrew/go)"

Make sure brew is up to date:

brew update

Install rbenv, ruby-build, and openssl:

brew install rbenv ruby-build openssl

Use rbenv to install Ruby 2.0

rbenv install 2.0.0-preview2

Special Cases

You may need to specify the location for the ssl directory:

CONFIGURE_OPTS=--with-openssl-dir=`brew --prefix openssl` rbenv install 2.0.0-preview2

You may also need to specify a different GCC

CONFIGURE_OPTS=--with-gcc=clang rbenv install 2.0.0-preview2

I highly suggest you install Ruby 2.0. There are some significant speed improvements and optimizations in the language.