I'd be surprised if Yahoo! doesn't use a custom search engine program. Have you checked the searching section at http://www.perlarchive.com/guide/Searching ? I'm not really clear what you want... please elaborate.
But what type? Do they use a data search through files? I know Yahoo has programmers to make that. But I want to get a script so I can learn freom it before I custon make my own.
MAIN
SEARCH
WHO'S 
LOG 