    abc_problem :-
            maplist(abc_problem, ['', 'A', bark, bOOk, treAT, 'COmmon', sQuaD, 'CONFUSE']).

    abc_problem(Word) :-
            L = [[b,o],[x,k],[d,q],[c,p],[n,a],[g,t],[r,e],[t,g],[q,d],[f,s],
                 [j,w],[h,u],[v,i],[a,n],[o,b],[e,r],[f,s],[l,y],[p,c],[z,m]],

            (   abc_problem(L, Word)
            ->  format('~w OK~n', [Word])
            ;   format('~w KO~n', [Word])).

    abc_problem(L, Word) :-
            atom_chars(Word, C_Words),
            maplist(downcase_atom, C_Words, D_Words),
            can_makeword(L, D_Words).

    can_makeword(_L, []).

    can_makeword(L, [H | T]) :-
            (   select([H, _], L, L1); select([_, H], L, L1)),
            can_makeword(L1, T).