In English we say ‘If you open the time portal, the raptors will escape!’ Which is fine, but not really. ‘If you open the time portal…’ sounds present tense, although it obviously isn't. Latin, which is far more exact(ing?) on this matter, has the future perfect tense. ‘If you will have opened the time portal, the raptors will escape!’ Which makes far more sense, because the raptors will not escape until a point in the future, in which the action of opening the portal has already been completed. The Future Perfect.
Marcellus noster is in a similar dilemma. Unless he will have given (dederit) one hundred dollars to the bank soon, it will be necessary for him to leave behind his home.
Unless Marcellus gives $100 to the bank soon, he will have to leave his home. Augustus, however, knows that he does not have the money.