> pkgsrc and autoconf are two (very) different beasts.
> 
> The user settable options for packages are described in
> pkgsrc/mk/bsd.pkg.defaults.mk.
> 
> USE_OPENSSL_VERSION is actually defined in pkgsrc/secruity/openssl/buildlink.mk
> 
> # Check for a usable installed version of OpenSSL.  Version must be greater
> # than 0.9.5a.  If a usable version isn't present, then use the pkgsrc
> # OpenSSL package.
> #
> .include "../../mk/bsd.prefs.mk"
> USE_OPENSSL_VERSION?=           ${OPENSSL_VERSION_095A}
> 
> # Associate OpenSSL dependency with version number.
> .if ${USE_OPENSSL_VERSION} == ${OPENSSL_VERSION_095A}
> BUILDLINK_DEPENDS.openssl=      {openssl-0.9.5a,openssl>=0.9.6}
> .else
> BUILDLINK_DEPENDS.openssl=      openssl>=0.9.6
> .endif
> 
> So USE_OPENSSL_VERSION is part of the buildlink functionality, and
> is meant to be used by package creators to specify a specific
> version of openssl to use in a package.

Thanks for clarification, I totally missed the mk/bsd.pkg.defaults.mk
file.  But I suspect that all the options for all the packages are
thoroughly listed in mk/bsd.pkg.defaults.mk...

Regards,
Masao