The verify(expr1, expr2, as_set) calling sequence is equivalent to the call verify({op(expr1)},{op(expr2)}, set).

The verify(expr1, expr2, as_set(ver)) calling sequence is equivalent to the call verify({op(expr1)}, {op(expr2)}, set(ver)).

The verify(expr1, expr2, as_set(ver, f)) calling sequence is equivalent to the call verify({op(expr1)}, {op(expr2)}, set(ver)) with  and .