You don't need to. If /sbin/init is mode (at least) 555 and
starts with the line "#!/bin/perl" (without quotes of course) and perl is really in /bin (no link) then this script will start as init. /usr/bin/perl doesn't work every time because /usr could be umounted.
If /usr is on a seperate fs, it would also require having /usr/lib/perl moved to /lib/perl; other library dependencies would have to be moved too...including any needed modules.
I've talked about this enough. I think I'm going to throw together a test system :D