[Zope] Getting access to additional-passed in variables from dtml

[VanL]

Hello,

I want to use dtml as a variable-substitution engine.  However, I'm not 
sure how to see what variables I have available.  For example, with page 
templates I can do the following:

<span tal:repeat="key python:options.keys()">
  <span tal:replace="key">The Key</span>
</span>

Is there an equivalent structure in dtml?

Thanks,

VanL