Which - things, namely, the three things handled, touched, and tasted.
are to perish - literally, “are constituted (by their very nature) for perishing (or ‘destruction by corruption’) in (or ‘with’) their using up (consumption).” Therefore they cannot really and lastingly defile a man (Mat 15:17; 1Co 6:13).
after - according to. Referring to Col 2:20, Col 2:21. All these “ordinances” are according to human, not divine, injunction.