A perpetual union that the states were not chained to. Rhode Island & Providence Plantations, or any state, could and did, foil any plan they disagreed with. Under the more perfect Constitution the majority of states could override a state "filibuster".
The word 'perfect' derives from the French term for improved (perfectionnement), as in "brevets d'importation et de perfectionnement" [patents for importation and improvement]. Which derived from the Latin parfit/perfectus, meaning "to finish". Basically, 'perfect' in todays vernacular would mean 'new and improved' or 'complete'.
'PERFECT. Something complete'.Not something perpetual.
Bouvier's Law Dictionary, Rev. 6th ed. (1856)
The Supreme Court said otherwise well before the war.
Even ol' Buck said so:
"In his final message to Congress, on December 3, 1860, James Buchanan surprised some of his southern allies with a firm denial of the right of secession. The Union was not "a mere voluntary association of states, to be dissolved at pleasure by any one of the contracting parties," said Buchanan. "We the People" had adopted the Constitution to form "a more perfect Union" than the one existing under the Articles of Confederation, which had stated that "the Union shall be perpetual." The framers of the National Government "never intended to implant in its bosom the seeds of its own destruction, nor were they guilty of the absurdity of providing for its own dissolution."
State Sovereignty was NOT superior to national sovereignty, Buchanan insisted. The Constitution bestowed the highest attributes of sovereignty exclusively on the federal government: national defense; foreign policy; regulation of foreign and interstate commerece; coinage of money. "This Constitution," stated the document, and the laws of the United States...shall be the supreme law of the land...anything in the constitution or laws of any State to the contrary notwithstanding."
-- Battle Cry of Freedom, James McPherson, p. 246
Walt