Set operations on email lists

I think someone should write an extension for Mailman or Majordomo to allow set operations like union (without duplicates) and intersect on mailing lists. Essentially things that SQL would support.
For instance, you have one list interns@company.com and another sf@company.com. To avoid having to maintain lists like interns-sf@company.com, you'd just write an email to interns%sf@company.com to reach all interns in the San Francisco office.
The API should be easy to remember, since people would manually compose these "queries" as part of the to-address in their email programs. Alternatively, there could be a web frontend (with live result preview, if subscriber lists are public) to make it easier to compose queries.
Another useful operation: rand(20,everyone)@company.com to send an email to 20 random people out of the whole company. There are definitely use cases where it would suffice to reach a few random people to answer a question without having to spam a huge list.

Now go implement it.