>> puts $:
/Library/Ruby/Gems/1.8/gems/mysql-2.8.1/lib
/Library/Ruby/Gems/1.8/gems/mysql-2.8.1/ext
/Library/Ruby/Site/1.8
/Library/Ruby/Site/1.8/powerpc-darwin10.0
/Library/Ruby/Site/1.8/universal-darwin10.0
/Library/Ruby/Site
/System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/lib/ruby/vendor_ruby/1.8
/System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/lib/ruby/vendor_ruby/1.8/universal-darwin10.0
/System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/lib/ruby/vendor_ruby
/System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/lib/ruby/1.8
/System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/lib/ruby/1.8/powerpc-darwin10.0
/System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/lib/ruby/1.8/universal-darwin10.0
.
=> nil