[Zope] Accesing a new context from a manipulated string

Here's my problem: given a method itemURL(), that typically returns a site relative URL such as '/about/', I need to change to the appropriate directories context using <dtml-with>. In short I need to do the equivalent of <dtml-with about>. The closest I've gotten so far is: <dtml-with expr="_.getitem(itemURL(), 0)"> which generates a KeyError: /about/ in the traceback. Can anyone help me truncate the extra '/'s off of this string and pass it to the <dtml-with>? Michael Bernstein.