How to separate the name in a variable in prolog?

I need to separate an entry into a variable in prolog, but I'm having trouble with that part:

nome(nome(X)) --> [X] :- X=[_].

conjuncao(conjuncao(e)) --> [e].

verb(verb(sou)) --> [sou].
verb(verb(come)) --> [come].
verb(verb(eh)) --> [é].
retorna_nome(periodo(per(S1,C,S2)) :-
noun_nome(nn(_))