Just Trust Me, Bro!

Split second (As long as this spell is on the stack, players
can’t cast spells or activate abilities that aren't mana abilities.)

Choose target spell with mana value X, then choose one or more:
— Perpetually remove any amount of text from target
spell.
— Perpetually replace one or more instances of “target” with “all” in target spell’s text
— Perpetually add the word “perpetually” to target spell’s text.