How to install a file outside of /usr/pkg ($PREFIX)

[Jose Luis Rodriguez Garcia <joseyluis%gmail.com@localhost>]

I am updating a pkgsrc package : mppe-lkm for that it works with NetBSD 6/7

I have to copy the kmod file to the /stand/../../modules/.. directory
for that the module can be loaded, and I don-t know what is the best
way.

I have tried to used the @cwd / sequence in the PLIST file, but
without sucess. It seems , that enve absolute pahts are relative to
/usr/pkg.

What alternatives do you suggest?