checking for eruby?

I installed mod_ruby like this:

$ ./configure.rb --with-apxs=/usr/sbin/apxs
$ make
# make install

It seems to work ok, but when it is configuring it reports this line:

checking for eruby... no

I have eruby installed and it seems to work just fine.

Is this just reporting that I didn't use this option or is it supposed to
automatically detect it?

--enable-eruby
--with-eruby-includes=DIR   
--with-eruby-libraries=DIR

What does --enable-eruby supposed to do?

Thanks,

Mark