[Zope] dtml-if Newbie Question

[Alfredo P. Ricafort]

Hi,

>From the 'Zope Book' the statement 
 
<dtml-if variable>

means that 'if the..variable does not exist, then this condition is
false'.

I found that this is not true.  When I tried using dtml-if to a
non-existent variable, I got a 'key error'. So how do I check if the
variable does not exist ?

Tks.

AL