Repeat With List
Repeat with variable in [x1, x2, x3, ...]
End Repeat
Additional Notes
From what I've been able to tell, the list must be explicity set when the Repeat is started. I haven't had any luck getting an arrray to work, and I haven't had any luck converting an array to work (without directly specifying the items).
It's quite frustrating, having a function which could step through an array would be very helpful.
As a possible comment on the usefulness of Repeat With List loops as currently implemented, there are none of these loops used in any of FCP's built-in filters.

