2jfw Er, that uses Pixelbender. Pixelbender was a marvellous addition to Flash, which enabled effects such as that. But Adobe deprecated it a long time ago, removing most or all of it from the runtime. AGAL in Stage3D largely superseded it, though AGAL was not as nice to work with as Pixelbender.
Now you could use Starling to do it. Render your page content into a texture, then create the 'page' as a 3D sheet with that texture applied, animating it to do the page turning. You can create the texture as a
RenderTexture in Starling, and animate the object as a