[Dovecot] SIEVE: Any information at all?

Hi,

I am quickly losing the will to live over the lack of any kind of information at all about the SIEVE support that is listed in the dovecot features list.
Does anyone have any information at all? I've grepped through the source, looked through all the configuration files, and googled a fair bit and come up with nothing at all.

How would a user with maildir enable a sieve script? Does it run on port 2000? How can I test functionality?

Thanks, Leah