Why not send in patches to all shells and OS distros so that we don't need a
PATH anymore, but
#!sh
#!perl
will just work (TM) and takes the one found first in $PATH
Ohhhhhh, such idylle
Come on! It's a Security Violation. Suppose the script is suid, and you have . in $PATH and a nasty ./sh - or something like that, I don't remember. There must be some exploit. It's useful, so it can't be safe.
