[etc]

package
{
	import flash.display.Sprite;
	public class Block extends Sprite
	{
		public function Block(keys:Array = null)
		{
			if(keys != null)
			{
				trace("ok");
			}
			else
			{
				var blockArea:Sprite = new Sprite();
				blockArea.graphics.lineStyle(1, 0x000000, 1);
				blockArea.graphics.drawRect(0, 0, 200, 200);
				addChild(blockArea);
			}
		}
	}
}

addChild(new Block());

Что не работает?