[eclipse 1]: delay(X, writeln(hello)). X = X Delayed goals: writeln(hello) yes. [eclipse 2]: delay(X, writeln(hello)), writeln(one), X=1, % causes waking writeln(two). one hello two X = 1 yes. [eclipse 3]: delay([X,Y], writeln(X)), X=Y. X X = X Y = X yes.