Rated 5 out of 5 stars

eyaler, thank you very much!
Complete instructions to duplicate the functionality:
1. Install userChromeJS v. 1.2 extension from userchromejs.mozdev.org, changing it to work on FF 4.
2. Put the code from the link pointed by eyaler in <your profile>/chrome/userChrome.js & delete the line "LOG ("copyHistory");"
3. Restart FF & enjoy