> > USE_OPENSSL_VERSION=0x0090602fL
> 
> Is this documented anywhere?

It's written in pkgsrc/security/openssl/Makefile.  Traditionally, *BSD
people seem to have thought that makefiles and sources are part of
document. :-)

> I've often been frustrated by learning (usually by some mailing list
> post) of options that can be used in mk.conf, but not being able to find
> them documented anywhere.  This frustrates me because I wonder how many
> other features/options I'm missing out on simply due to not knowing
> about them.

Pkgsrc definitely lacks an interface to show such options to users.
Autoconf does better in this point.

Regards,
Masao