Using a Bounce Expression?

I animated a .png of an item falling, and rotating as it falls until it hits the floor. After the animation ended, I moved the CTI a few frames ahead and rotated it a bit to add a new keyframe, and moved the CTI again and rotated it again to make it seem more like a bounce when it hit the ground. I want to make the bounce seem a bit more natural. I spent some time online and I read about Expressions, and I copied some Bounce Expression that I found, and I want to paste it so I press alt and clicked on the Stopwatch for  Rotation to paste the Expression since this is the last thing that I added to the animation. The Expression editor opens with

transform.rotation

When I paste the following Bounce Expression after this it just gives me an error.

“This project contans an expression error: error 1 of 1. What am I doing wrong? Thanks in advance!

e = .5;

g = 20000;

nMax = 9;

n = 0;

if (numKeys > 0){

n = nearestKey(time).index;

if (key(n).time > time) n–;

}

if (n > 0){

t = time – key(n).time;

v = -velocityAtTime(key(n).time – .001)*e;

vl = length(v);

if (value instanceof Array){

vu = (vl > 0) ? normalize(v) : `{`0,0,0`}`;

}else{

vu = (v < 0) ? -1 : 1;

}

tCur = 0;

segDur = 2*vl/g;

tNext = segDur;

nb = 1; // number of bounces

while (tNext < t && nb <= nMax){

vl *= e;

segDur *= e;

tCur = tNext;

tNext += segDur;

nb++

}

if(nb <= nMax){

delta = t – tCur;

value + vu*delta*(vl – g*delta/2);

}else{

value

}

}else

value