# File lib/compass/sass_extensions/functions/constants.rb, line 49
    def is_url(string)
      if string.is_a?(Sass::Script::String)
        is_url = !!(string.value =~ /^url\(.*\)$/)
        Sass::Script::Bool.new(is_url)
      else
        Sass::Script::Bool.new(false)
      end
    end