Well, I'm looking for an addon that can redirect a link when I click on it in the following ways:

1. Change from https to http
2. Change from twitter.com/xxxxxxxxx to, for example, dabr.co.uk/xxxxxxxxx
3. (added at 2010-02-15th, 20:30 GMT) Remove the "?utm_source=twitterfeed&utm_medium=twitter" from the end ou a URL
4. Generally, replace a string with another (e.g. youtube->yt; so www.example.com/visitingyoutube would become www.example.com/visitingyt)

PS: (added at 2010-02-15th, 20:30 GMT) @oKtosiTe, a clearer user case:

1. Supposes that there is a link in Twitter that point to a URL X (URL X is http://www.newspapersite.com/2011-02-15_1304.html?utm_source=twitterfeed&utm_medium=twitter)
   
2. In that case, I want to open that URL only until ".html", i.e., I want to open a URL Y, that is http://www.newspapersite.com/2011-02-15_1304.html
   
3. What happens when I click normally in that link:
   3.1. Browser goes to URL X
   
4. What I want to happen when I click in that link:
   4.1. The addon must transform URL X to URL Y (I must configure it before to change a piece of URL from "?utm_source=twitterfeed&utm_medium=twitter" to ""
   4.2. The browser goes to URL Y