delete messages from the command-line?

[mikee]

I use deliver to put messages directly into the inbox
or some folder inbox.folder. Is there a similiar way
to remove messages from a folder? I want to remove messages
when a folder has more than 1000 messages or the messages
are older than four days.

I don't want to remove the messages using something
from root's cron for fear of messing up the indexes
or caches inside cyrus.

Mike