module ActionView

module AbstractController

module Rendering
  def render_to_body_with_haml(options = {})
    if rendered = render_to_body_without_haml(options)
      rendered.gsub('<haml:newline/>', "\n").html_safe
    end
  end
  alias_method_chain :render_to_body, :haml
end

end

This module refers to the ActionView module that's part of Ruby on Rails. Haml can be used as an alternate templating engine for it, and includes several modifications to make it more Haml-friendly. The documentation can be found here.