Internet is very confusing source of info, well, sometimes.
A search for Piper longum L. gives plant pictures of distinctly variable leaf venation, even scanned herbarium images available in the net can be confusing too. Two such example :-
Bengali Name : PIPUL
Habit & Habitat : wild slender creeper, growing under very dense vegetation of, i think, Mikania micrantha Kunth.
Date : 21/9/12, 4.02 p.m.
Place : Garalgacha (Hooghly)
I am sorry that my camera is a dumb under low light.
Thank you & Regards,