Show me the provision of the United States Constitution, not the Articles of Confederation or any other document but the Constitution, making reference to a "Perpetual Union" and I'll utter not one more word on this subject!
OK, quoting again from Chief Justice Chase's decision:
"The Union of the States never was a purely artificial and arbitrary relation. It began among the Colonies, and grew out of common origin, mutual sympathies, kindred principles, similar interests and geographical relations. It was confirmed and strengthened by the necessities of war, and received definite form, and character, and sanction from the Articles of Confederation. By these the Union was solemnly declared to "be perpetual" And when these articles were found to be inadequate to the exigencies of the country, the Constitution was ordained "to form a more perfect Union." It is, difficult to convey the idea of indissoluble unity more clearly than by these words. What can be indissoluble if a perpetual Union, made more perfect, is not? "
But I hasten to add that the Chief Justice made it clear that there was a way for a state to peacefully leave the Union and I quoted that earlier. "The union between Texas and the other States was as complete as perpetual, and as indissoluble as the Union between the original States. There was no place for reconsideration, or revocation, except through revolution, or through consent of the States.
With the consent of the states, same way all but the original 13 states entered the Union. The south should have tried that.