Now that is another can of worms.
Isn't it though.
If the union was perpetual, how did the present Constitution come about?
Apparently, the States saw that the "general government" they had established was not working that well, and their delegates convened to come up with "a different organization". Note the following: The friends of our country have long seen and desired, that the power of making war, peace, and treaties, that of levying money and regulating commerce, and the correspondent executive and judicial authorities should be fully and effectually vested in the general government of the Union: But the impropriety of delegating such extensive trust to one body of men is evident-Hence results the necessity of a different organization. (Letter of the President of the Federal Convention, Dated September 17, 1787, to the President of Congress, Transmitting the Constitution.) They appear to have not been talking about dissolution, but about a new "arrangement" among them.
Some States ratified the new Constitution readily. Others under some political pressure.
True enough as far as I know. Arguably, the States imposing political pressure could have felt justified in doing so because they were applying pressure to get compliance with a previous agreement (Perpetual Union). Maybe not quite the same but similar to your spouse pressuring you to stop fooling around because you agreed to be faithful. (I don't know if I'll stand by that analogy. It just popped out.)
Did not those States which first ratify the Constitution simultaenously secede from the perpetual union.
I believe ratification by 9 states was necessary before the Constitution took effect upon the states that had ratified. Nine being the majority, I assume they would have thought that those nine were the true heirs of the Perpetual Union.