http://www.alistapart.com/articles/perl/ is one (written by a monk, jryan) and it's good basic/learning code for a small site. It would drag on anything big or busy. But by that time you will have learned how to do indexing in some kind of DB in various idioms. :)

• http://www.perl.com/pub/a/2003/09/25/searching.html
• http://www.perl.com/pub/a/2003/02/19/engine.html

Search for "reverse index," "vector search," and things like "'site search' perl" on Google and in the Super search for lots more.

PS: $/... You keep using that variable. I do not think it means what you think it means.