What is this for? You can use the search API directly (it works with URLs):<p><a href="http://apiwiki.twitter.com/Twitter-API-Documentation" rel="nofollow">http://apiwiki.twitter.com/Twitter-API-Documentation</a><p>If you truly want regex support, just grab a lot of tweets with the API, and filter client-side.
Twitter clients on the desktop suck.<p>yorufukurou does regex and is generally tolerable (OS X)
<a href="http://sites.google.com/site/yorufukurou/home-en" rel="nofollow">http://sites.google.com/site/yorufukurou/home-en</a><p>Apart from that, it's easy to roll your own stuff - for example using the tweepy python library.
BYO with Yahoo BOSS. Here's an example app:
<a href="http://zooie.wordpress.com/2009/01/15/twitter-boss-real-time-search/" rel="nofollow">http://zooie.wordpress.com/2009/01/15/twitter-boss-real-time...</a>