libmail-verp-perl ソースパッケージをダウンロード:
Mail::Verp provides utility functions to encode and decode Variable Envelope Return Paths (VERP) addresses, as described by http://cr.yp.to/proto/verp.txt.
VERP addresses are used to help manage bounces coming back from remote SMTP servers, especially when dispatching mail for a mailing-list; the VERP address encodes the recipient address, which can then be recovered from the bounce to unsubscribe the address from the mailing-list.
The encoding uses the method described by http://www.courier-mta.org/draft-varshavchik-verp-smtpext.txt.