The idea that the same people who made the Perpetual union would have then changed it to "Well, any time someone breaks a nail or has a bad hair day they can unilaterally pull out," well, is to laugh.
So what you’re saying is that the States had the right to refuse to become a part of the Union, but once a part of that Union, they gave up their individual rights as soverign States? How very fascist of you.