[Zope] how to set value of hidden form field by a cookie

I've to set the value of a hidden form field by a cookie value. e.g; invalidval request/cookies/login|nothing; i tried this : <input name="invalid" type="hidden" value="string: ${invalidval}"> and also this <input name="invalid" type="hidden" tal:attributes="value invalidval"> but it is rendering the text in quotes directly. what is the correct way. -- Share the vision of difference with ME