# File lib/sass/script/tree/variable.rb, line 47
    def _perform(environment)
      val = environment.var(name)
      raise Sass::SyntaxError.new("Undefined variable: \"$#{name}\".") unless val
      if val.is_a?(Sass::Script::Value::Number) && val.original
        val = val.dup
        val.original = nil
      end
      val
    end