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)
ruby -e "$(curl -fsSkL raw.github.com/mxcl/homebrew/go)"
Make sure brew is up to date:
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
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
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.
Seth Vargo is an engineer at Google. Previously he worked at HashiCorp, Chef Software, CustomInk, and some Pittsburgh-based startups. He is the author of Learning Chef and is passionate about reducing inequality in technology. When he is not writing, working on open source, teaching, or speaking at conferences, Seth advises non-profits.