If Transform isn't available, make a duplicate layer and try again.
If Transform isn't available, do a Select All <Ctrl A>, to make it come out.
Perspective transformation can also be made with a crop.
Yet another way to do it is to use the Distort transform instead of Perspective. Distort offers additional adjustments that can be handy if the camera was not level or if the desired correction is of an object at an oblique angle to the camera....
Any of the transform options can also be used to exaggerate and distort as well, though these are outside the scope of my question on ethics: about making perspective corrections in landscape photos of natural objects, not buildings.[/font]