You lens alone will not change perspective. One thing truly affects perspective: your location relative to what you are shooting. That is what perspective means, after all. If you put a camera on a tripod and take the same picture with many different lenses, without moving the camera between shots, the perspective does not change. The angle of view changes.
Using different lenses from the same point simply to obtain the desired angle of view will not change perspective. However, changing focal lengths quite often causes a change in location of the camera, so it is often stated that lenses themselves change perspective. Try zooming in and walking backward simultaneously (or vice versa) at a rate that keeps a foreground subject the same size throughout. Then try just standing in one place and zooming in and out. Big difference between the two!
To me, a normal lens is the lens that you use when you want to shoot from the standard eyeball viewing distance from something without heavily distorting the relative locations of objects within the frame. That means that if I put the camera up to one eye, the sizes and locations of objects look the same as I see them with my other eye.
I think my 55mm works as a slightly more "true" normal lens than my 50mm. I find myself often having to move slightly closer with a 50 to get the shot that originally caught my eye before raising the camera, since everything shrinks a bit when I raise the 50 to my eye. I think a 58mm would be even slightly more close than my 55. The 55 shrinks things just a teeny bit; almost not noticeable.
I love normal lenses for their ease and quickness of composition. You see something, you raise the camera, and you pretty much already have the composition.
