[Zope] Redirect from zpt

Where do I go to search the archives of this list? I need to redirect from a zpt to another page, if request does not have a specific key. I have googled and read the zope book and tried every variation I can think of... now I just feel stupid. How do I get a tal:condition to call response.redirect if request.has_key(myval) is false ? -- Les Ferguson Software developer Waitakere, NZ