knoppix@Microknoppix:~$ perl -Mstrict -Mwarnings -E '
> my $line = q{May  2 04:06:15 lon-pop.mail.mydom.com pop3login: LOGOUT, user=gonenow, ip=[::ffff:127.0.0.1], top=0, retr=0, rcvd=24, sent=5560, time=1};
> my ( $mon, $day, $time, $dom, $login, $remainder ) =
>    split m{:?\s+}, $line, 6;
> my %monthNos = do {
>    my $no = 0;
>    map { $_ => ++ $no }
>    qw{ Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec };
>    };
> 
> my $yr = q{2012};
> my $csv = sprintf q{%02d/%02d/%s %s,%s,%s,%s},
>    $day, $monthNos{ $mon }, $yr, $time, $dom, $login, $remainder;
> 
> say $csv;'
02/05/2012 04:06:15,lon-pop.mail.mydom.com,pop3login,LOGOUT, user=gonenow, ip=[::ffff:127.0.0.1], top=0, retr=0, rcvd=24, sent=5560, time=1
knoppix@Microknoppix:~$