private var mousePVec:b2Vec2 = new b2Vec2();
private var mouseJoint:b2MouseJoint;
private var mouseXWorldPhys:Number;
private var mouseYWorldPhys:Number;
private var isMouseDown:Boolean = false;

 
private function setupMouseEvents():void
{
	stage.addEventListener(MouseEvent.MOUSE_DOWN, onMouseDown);
	stage.addEventListener(MouseEvent.MOUSE_UP, onMouseUp);
}
 
private function onMouseDown(e:MouseEvent):void{isMouseDown = true;};
private function onMouseUp(e:MouseEvent):void{isMouseDown = false;};
 
private function updateMouseWorld():void{
	mouseXWorldPhys = mouseX/WORLD_SCALE; 
	mouseYWorldPhys = mouseY/WORLD_SCALE; 
}
 
private function mouseDrag():void{
	// mouse press
	if (isMouseDown && !mouseJoint){
 
		//refer to 'getBodyAtMouse()' below
		var body:b2Body = getBodyAtMouse();
 
		if (body)
		{
			var md:b2MouseJointDef = new b2MouseJointDef();
			md.body1 = world.m_groundBody;
			md.body2 = body;
			md.target = new b2Vec2(mouseXWorldPhys, mouseYWorldPhys);
			md.maxForce = 300.0 * body.m_mass;
			md.timeStep = timeStep;
			mouseJoint = world.CreateJoint(md) as b2MouseJoint;
			body.WakeUp();
		}
	}
 
	// mouse release
	if (!isMouseDown){
		if (mouseJoint){
			world.DestroyJoint(mouseJoint);
			mouseJoint = null;
		}
	}
 
 
	// mouse move
	if (mouseJoint)
	{
		var p2:b2Vec2 = new b2Vec2(mouseXWorldPhys, mouseYWorldPhys);
		mouseJoint.m_target = p2;
	} 
}
 
public function getBodyAtMouse(isStaticIncluded:Boolean=false):b2Body{
	// Make a small box.
	mousePVec = new b2Vec2(mouseXWorldPhys, mouseYWorldPhys);
	var aabb:b2AABB = new b2AABB();
	aabb.lowerBound = new b2Vec2(mouseXWorldPhys - 0.001, mouseYWorldPhys - 0.001);
	aabb.upperBound = new b2Vec2(mouseXWorldPhys + 0.001, mouseYWorldPhys + 0.001);
 
	// Query the world for overlapping shapes.
	var maxCount:int = 10;
	var shapes:Array = new Array();
	var count:int = world.Query(aabb, shapes, maxCount);
	var body:b2Body = null;
	for (var i:int = 0; i < count; ++i)
	{
		var shape:b2Shape = shapes[i] as b2Shape;
		var inside:Boolean = shape.TestPoint(shape.m_body.GetXForm(), mousePVec);
		if (inside)
		{
			body = shape.m_body;
			break;
		}
	}
	return body;
}

override protected function onRenderTick(event:Event=null):void
{
	updateMouseWorld();
	mouseDrag();
[...]