* closes non-focused tabs;
* indicates number of duplicates on toolbar button and shows the list on button's tooltip;
* hides the button when there are no duplicates (optionally);
1) After installing, reload all opened tabs so that the extension could access them.
2) Closing and counting of Speed Dial, Opera Mail, Opera Add-Ons and other service tabs may NOT be possible because of limitations in Opera Extensions API.
3) To be able to close secure and private tabs make sure you've turned on corresponding options in Privacy settings (Menu -> Extensions -> Manage Extensions -> No Dupes -> <wrench icon> -> Privacy)