Variable Envelope Return Paths (VERP) address encoder/decoder

 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.