# File lib/rack/mount/vendor/regin/regin/expression.rb, line 75
    def to_s(parent = false)
      if parent || !options?
        map { |e| e.to_s(parent) }.join
      else
        with, without = [], []
        multiline ? (with << 'm') : (without << 'm')
        ignorecase ? (with << 'i') : (without << 'i')
        extended ? (with << 'x') : (without << 'x')

        with = with.join
        without = without.any? ? "-#{without.join}" : ''

        "(?#{with}#{without}:#{map { |e| e.to_s(true) }.join})"
      end
    end