instiki/vendor/rails/actionpack/lib/action_view/template_handlers/builder.rb

require 'builder'

module ActionView
  module TemplateHandlers
    class Builder < TemplateHandler
      include Compilable

      def compile(template)
        "_set_controller_content_type(Mime::XML);" +
          "xml = ::Builder::XmlMarkup.new(:indent => 2);" +
          "self.output_buffer = xml.target!;" +
          template.source +
          ";xml.target!;"
      end
    end
  end
end