:- dynamic(solution/1).

:- use_module(library(reif)).
:- use_module(library(iso_ext)).
:- use_module(library(debug)).

foo(1).
foo(2).
bar(3).

findn(Vars0, Goal0, Result) :-
    retractall(solution(_)),
    assertz(solution([])),
    copy_term_nat(Goal0, Goal),
    term_variables(Goal, Vars),
    (collect_solutions(Vars, Goal); true),
    solution(Result).

collect_solutions(Vars, Goal) :-
    call(Goal),
    write(Vars),
    retract(solution(S0)),
    assertz(solution([Vars | S0])),
    false.