This implement a large majority of OpenSSL's useful X509 API. The email() method supports both certificates where the subject is of the form: "... CN=Firstname lastname/emailAddress=user@domain", and also certificates where there is a X509v3 Extension of the form "X509v3 Subject Alternative Name: email=user@domain". WWW: http://search.cpan.org/dist/Crypt-OpenSSL-X509/