[Zope] DTML to search a lines property in a DTML Document?

Can you, using DTML, search a lines property of a DTML Document to look for a specific string? I have a set of DTML Documents with a custom lines property (called, e.g., "doctrines") and I want to search through the list in the context of a conditional statement in order to filter out the DTML Documents that don't have a specific doctrine in the doctrines property (or list those that do). Has anyone ever done that or something similar? TIA, Ron