Getting the ${PREFIX} right

["Jesper Louis Andersen" <jlouis_(_at_)_mongers_(_dot_)_org>]

This seems to be a difference between the OpenBSD ports tree and the
NetBSD ditto: When netbsd has to mangle the ${PREFIX} location in 
a pkg, they patch the source-tarballs makefile with:

-BINDIR=whatever
+BINDIR=${PREFIX}/bin

At least audio/ascd in the OpenBSD ports tree does patch in

+BINDIR=%%PREFIX%%/bin

and then adds a post-patch target to the port Makefile with a call
to sed(1):

post-patch:
        @sed -e "s:%%PREFIX%%:${PREFIX}:g" \
                ${WRKSRC}/misc/config.h.default > ${WRKSRC}/config.h
...

Now the questions are:

What are the correct thing to do in an OpenBSD port? The latter I
presume, but I want a confirmation. I searched via google and a
``site:www.openbsd.org PREFIX'' but found nothing interesting about
it. I am aware that google doesn't go that deep on sites.

Is this stuff that should be listed on 

http://www.openbsd.org/porting/diffs.html

or maybe in other places at the port documentation?

-- 
jlouis