Dec 12
To find where a particular ruby gem lives, use this:
> gem1.9 which haml (checking gem haml-2.2.15 for haml) /usr/local/lib/ruby1.9/gems/1.9.1/gems/haml-2.2.15/lib/haml.rb
> gem1.9 which haml (checking gem haml-2.2.15 for haml) /usr/local/lib/ruby1.9/gems/1.9.1/gems/haml-2.2.15/lib/haml.rb