    # File lib/merb-core/controller/template.rb, line 177
        def register_extensions(engine, extensions)
          raise ArgumentError, "The class you are registering does not have a compile_template method" unless
            engine.respond_to?(:compile_template)
          extensions.each{|ext| EXTENSIONS[ext] = engine }
          Merb::AbstractController.class_eval "include \#{engine}::Mixin\n"
        end