int i = 0;
    while (i < 5) {
        i = i+1;
        printf("i: %d\n", i);
    }

    let i = 0 in
        whileM (pure (i < 5)) $
            let i = i + 1 in
                printf "i: %d\n" i

(And as GP points out, i=i+1 is an infinite loop in Haskell. But even if it was used to build a lazy structure, it would just keep running the same iteration over and over because when the block is entered, i still has the value that was set outside.)