Regex links

Regex (regular expresssion) is referred to as 正規表現（せいきひょうげん） in Japanese. And people like to say that Japanese technical language is all straight from English. I think not.

www.silveragesoftware.com has some nice explanations.

There's a sample chapter of Jeffrey Friedl's Regex book.

This page on applying url redirects in Apache gave me some hints on how to write the regex I wanted.

This regex testing page let me test out my expression:
.+\.(bmp|gif|jpg|jpeg|png)$

Basically I need to only allow files with the above extensions.