The goal of this guide is to get up and running with a las3r repl as quickly as possible. We should end up with a .swf file that displays a REPL when run. Here's the main class for our simple AS3 project:

package {
  import flash.display.Sprite;
  import com.las3r.repl.Repl;

  public class Las3rTest extends Sprite {
    public function Las3rTest() {
      var repl:Repl = new Repl(500, 400, stage);
      stage.addChild(repl);
      repl.evalLibrary("(defn say-hello [] (println 'Hello World'))");
    }
  }
}

Next, grab the las3r.swc from the dist folder of the las3r distribution. Assuming we've got the Flex tools installed, we can now compile our SWF.

mxmlc -library-path+=PATH_TO_SWC/las3r.swc Las3rTest.as

You should now have Las3rTest.swf. Launch this SWF and you'll see a las3r repl.
Input (say-hello) and press enter to call the function we defined.

Have a look at the core library for more functions.