Copy selection to clipboard automatically

I am looking for a program that can copy any selected text to the clipboard automatically. E.g. if I select some text in Safari or Eclipse, it should automatically copy it to the keyboard.

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The Google Chrome extension Auto Copy 3.0.3 can do it in Google Chrome.

The application PopClip displays a popover menu which appears when some text is selected in any application but there doesn't seem to be any way to automatically copy it to the keyboard.