Pattern matching: HELP! 2

[email protected] Tue, 23 Apr 2002 18:03:44 CEST
Newsgroups perl.macperl.anyperl
Message-ID <20020423160344.BRJ26613.fep49-svc.tin.it@[127.0.0.1]>
I need to extact the user name of every user who is logged in /var/log/maillog.I just want the user name and every one must be present just one time.
Now I can extract all the strings with the user name and every name is repeated many times.What can I do?Thanks a lot