# File lib/sass/tree/debug_node.rb, line 24
      def _perform(environment)
        res = @expr.perform(environment)
        res = res.value if res.is_a?(Sass::Script::String)
        if filename
          $stderr.puts "#{filename}:#{line} DEBUG: #{res}"
        else
          $stderr.puts "Line #{line} DEBUG: #{res}"
        end
        []
      end