Mosiah 27:29 is a classic example of parallellism, a Hebrew form of poetry. One idea is repeated twice with different words:
"I was in the darkest abyss; but now I behold the marvelous light of God.
My soul was racked with eternal torment; but I am snatched, and my soul is pained no more."
My soul was racked with eternal torment; but I am snatched, and my soul is pained no more."
On a more theological note, how can one be racked with eternal torment and then be snatched out of it? Compare with D&C 19
"10 For, behold, the mystery of godliness, how great is it! For, behold, I am endless, and the punishment which is given from my hand is endless punishment, for Endless is my name. Wherefore
11 Eternal punishment is God’s punishment."