🚀 go-pugleaf

Would someone please tell me what is going on?

(I am just starting to use prolog, and was looking for a 
compiler/interpreter, so I downloaded the stuff from cs.arizona.edu
(/sbprolog/v3), and installed it.
....... Unlike some others, I did not have any problems here. )

Now, I want to use it. Could someone please tell me how to
start up the interpreter and do something/anything (even a query like 2=3 is
fine). (The manual I have gives the following instructions:--

       sbprolog <bc_file>

where <bc_file> is the file $readloop in the modlib directory, i.e.,

       sbprolog <path>/modlib/'$readloop'  .

Anyway, the program does not complain about a missing $readloop file, so
I guess it has found it. However, this is what happens:
----------------------------------------
% sbprolog '../modlib/$readloop'

Halt. Program terminated normally
----------------------------------------
and that is that. Now this would be fine if I had actually tried to run a
program, but the poor guy is only just trying to get started.

I will appreciate any help at all. Thanks.