It sounds like that's what Joel is asking. I don't know of a good way to do this all in a single Assign Tokens or Pattern Match activity. Laserfiche just uses Microsoft's .NET style regular expressions, but I don't believe there is any support for the "replacement" features within the token dialog. (You could use those options within some kind of .NET script if you chose). I think your best bet to make a workflow that is understandable and easy to maintain is to rearrange the date by using multiple tokens and piecing them together.

Of course, there are ways to do it, if you really want to force things without any regard to how clumsy the expressions will get. For instance, the first option I thought of was that you could use a pattern match where the input is your date token duplicated as many times as necessary, and then you could use capture groups to pick off the pieces in a new order.  Say you had dates in dd/mm/yyyy format and wanted to switch the day and month. You could use "%(your_date)%(your_date)" as input, and then match this with something ugly like "\d{2}/(\d{2}/)\d{4}(\d{2}/)\d{2}/(\d{4})" which just picks off the groups you want in the new order. Again, I would strongly recommend against this because it would probably be terrible to try and figure out why/how this all works if you come back to the workflow several months later for some reason.