Perspective

Perspective is the relative change of size of subjects at different distances to the camera.

Perspective changes with the distance to the subject. Changing the focal length does not change the perspective, only the angle of view. To change only the perspective you must change both the distance and the focal length so the subject is framed identically from a different distance.

The further away from the subject the smaller will the angular size of the subject be and the smaller wille the difference be between subjects at different distances.

At extremely long distances the perspective becomes completely flat and there is no difference in size between subjects at different distances.