# File lib/rack/utils.rb, line 201
    def delete_cookie_header!(header, key, value = {})
      unless Array === header["Set-Cookie"]
        header["Set-Cookie"] = [header["Set-Cookie"]].compact
      end

      header["Set-Cookie"].reject! { |cookie|
        cookie =~ /\A#{escape(key)}=/
      }

      set_cookie_header!(header, key,
                 {:value => '', :path => nil, :domain => nil,
                   :expires => Time.at(0) }.merge(value))

      nil
    end