Relevance Blog : Working With Multiple Ruby Versions Has Never Been This Easy
http://blog.thinkrelevance.com/2009/7/29/ruby-switcher-working-with-multiple-ruby-versions-has-never-been-this-easy

echo "source ~/ruby_switcher.sh" >> .bash_profile

http://github.com/spicycode/beholder

ruby_switcher 여러 버전의 루비를 명령하나로 바꿔가면서 사용할 수 있다

Nice post and accompanying bash script to manage multiple versions of ruby.