[Zope] dtml-var weirdness

Hi everyone, Stupid question of the day: Why might the following code result in a KeyError? It does in some contexts under Zope 2.5.0. <dtml-if expr="REQUEST.has_key('xyz')"> <dtml-else> <dtml-call expr="REQUEST.set('xyz','Hello world')"> </dtml-if> Sometimes the next line results in a KeyError, value 'xyz': <dtml-var name="xyz"> In such cases, this works fine: <dtml-with REQUEST only> <dtml-var name="xyz"> </dtml-with> Huh? TIA, -- Joe "I should like to close this book by sticking out any part of my neck which is not yet exposed, and making a few predictions about how the problem of quantum gravity will in the end be solved." --- Physicist Lee Smolin, "Three Roads to Quantum Gravity"