tween is an actionscript class and can be used after importing the core files.

[code lang=”actionscript”]
import mx.transitions.Tween;
import mx.transitions.easing.*;
//Tween( obj:Object, prop:String, func:Function, begin:Number, finish:Number, duration:Number, useSeconds:Boolean);
[/code]

e.g.
[code lang=”actionscript”]
var myRot:Tween = new Tween(myText, “_rotation”, Elastic.easeOut, 0, 360, 3, true);
[/code]