To run the Substitution Model, load the file "load-submodel.scm" in MIT
Scheme.  (It should run fine on the athena version.)  Then evaluate

                          (smeval '<expression>)
or
                    (smeval '(<defines> <expression>))
to display the successive steps as the expression or body rewrites.

The file "examples.scm" contains a selection of Scheme expressions which
have been used to illustrate and test the submodel evaluator.

The file "prntless.scm" contains some extra filtering procedures for
getting more concise output.