need scripting help for notorius comment spammer

i have located the comment source script, comment.inc

i want to limit the string-sequence "[url]" to just ONCE per comment, otherwise to close the screen silently.
(ok i know it is required twice, [/url])

i have books about php...but it would take me a while to clamp-in a few lines to deactivate a notorious porno comment spammer.

if you can help out?

by the way here the gallery url, maybe you can encounter the spammer's latest comments: http://mio5.net/gallery

the same rubbish comments are also added notoriously to groups on http://g.hatena.ne.jp, for instance
http://ecrafts.g.hatena.ne.jp/

each time a spam comment is added, one particular diary bounces to the top.

i think this shall not pass un-noticed.
for my part now i ask here for script help to prohibit more than one URL per comment.

the products (imitation watches, penterpene, viogra, ringtones, hardcore movies) are not wanted by anyone.