class Haml::Buffer

def underscore(camel_cased_word)

but copied here so it'll run properly without Rails.
Based on the method of the same name in Rails' Inflector,
Changes a word from camel case to underscores. 
def underscore(camel_cased_word)
  word = camel_cased_word.to_s.dup
  word.gsub!(/::/, '_')
  word.gsub!(/([A-Z]+)([A-Z][a-z])/, '\1_\2')
  word.gsub!(/([a-z\d])([A-Z])/, '\1_\2')
  word.tr!('-', '_')
  word.downcase!
  word
end