Try the following problems after typing 
(consult "~/SEQUEL/FRAMEWORKS/MIX/mix.fr") and (prooftool) to the SEQUEL
top level. 

Problem 1;

1> ok

CONCLUSION

?- ((append (cons 1 (cons 2 nil)) place-holder-1) = answer?)

MIX>> PARTIAL-EVALUATOR 1000

Problem 2;

1> ok

CONCLUSION

?-  ((unify (cons 1 (cons 2 nil)) place-holder-1 nil) = answer?)

MIX>> PARTIAL-EVALUATOR 10000
