According to users, the add-on inserts two buttons into the system keyboard -- one for copying and another for pasting. Those who have tried it out say that it only accepts user-entered text and copies over one line at a time, which can get cumbersome.
Sebastien over at the iPhone Download Blog gives a detailed overview of how the application works. "After installing the application, type any text you want and simply hit the "123″ button on your keyboard to show the copy/paste buttons. Tap "copy" and start selecting the text you want to copy. Tap "copy" again to end the selection. Then tap "paste" to paste this text where you want it to be." This implementation isn't up to Apple's standards for grace and ease, but it seems workable.
My iPhone isn't jailbroken, so I haven't had the chance to try out Clippy. If you've downloaded and had a chance to try out the app, please let us know your impression in the comments.
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