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.