; Active (call-by-value) tuples defined for compilability:
(ft (tup) `(tup))
(ft (tup _first | _rest) `(tup _first | _rest))

; Most general unifier
(ft (mgu _x _x) _x)

; One of the following pause clauses should always be commented out:
;(hn (pause))            ; no manual dialog steps in exec (pure batch use)
(hn (pause) (relfun)) ; manual dialog steps in exec (semi-interactive use)