🚀 go-pugleaf

While browing through some vm5 code yesterday, I happened upon the notion 
of a virtual folder.  Looked like a neat idea that I could use to sort
some of hte mail I get (mostly stuff that needs to go into multiple
categories).  

The problem is that the doco on virtual folders is, well, a bit sparse.
Obviously I'm screwing things up somewhere, I'm just not where where.

Has anyone used virtual folders?  Could someone ship me a quick example 
(even, or especially, if it is a fairly hairy one)?

Thanks!

Ed King