Convert underscores to dashes with Apache mod_rewrite

Update: (Aug 4 2007) the stuff below is no longer necessary, all major search engines now treat underscores and dashes exactly the same, as word separators!

A year or so back, I was using underscores in my URL's on this site for spaces, and I decided to switch them to dashes, since several people, including Matt Cutts, had blogged that this was "the way to go". Now at that time I just redirected all old URL's to new ones, which created like 30 lines in my Apache config, something I didn't really like...

This morning I took the time to find a more elegant solution, and the easiest one I could come up with is the following:

RewriteCond %{REQUEST_URI} ^(.*)_(.*)/$
RewriteRule (.*)_(.*)/ http://yoast.com$1-$2/ [R=301]

This will rewrite a single underscore to a single dash, using a 301 redirect. So if you have directories with four underscores, it will go through this rewrite four times before reaching the final URL. I had some directories in which this was the case, and made sure it only had to redirect a maximum of two times by adding the following lines above it:

RewriteCond %{REQUEST_URI} ^(.*)_(.*)_(.*)/$
RewriteRule (.*)_(.*)_(.*)/ http://yoast.com$1-$2-$3/ [R=301]

You could add even more lines like these if need be, I'd make sure that no more than two redirects are needed to rewrite the underscores into dashes.

The "/" on the end of the RewriteCond is there to make sure this is a directory, and not a file, since I've got quite a few images with underscores in the names and didn't want to bother renaming them.