I think Darin's example of the pencil point aligned with the mountaintop (or not) is more an example of changing the "viewpoint" than the "perspective". The viewpoint is where you see something from. When you change the position of the lens, you change the viewpoint.
"Perspective" and "viewpoint" may be synonyms for, say, political writing, but have different meanings in photography and art.
In art, "perspective" usually refers to the rules of artificial one- two- three- or four-point perspective systems to simulate natural perspective, or a method of violating those rules, (as in M. C. Escher's work).
In view camera photography, "perspective" generally refers to how straight lines from natural perspective align in the rectangle of the frame, and "perspective control" traditionally refers to using the swings and tilts to "correct" the perspective of converging lines that one wants parallel to the frame edges, or similar distortion. This is also the reason for "perspective control lenses" for non-view camera photography.
And while camera movements can also be used to effect the focus, that doesn't fall under the area of "perspective control", even though it often does affect perspective.
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