I did a mistake: I don't know how, but I moved many views from tabs to others. (for instance, "package explorer" is in the right-side instead of left, ...)
Do you know if I can do an "undo" (like a ctrl-z or winner-undo for emacs) to come back in a previous view/perspective configuration ?
precision : I don't want to reset the layout to a default perspective.
AFAIK, there's no 'undo' for view move, but you can select the tabs and drag them wherever you want in the perspective (except in the editors area).