Some of the features of masks in Degrafa go beyond what is offered as regular masking support in the Flash Player. With masks in Degrafa you can define a shape via Degrafa MXML and mask another Degrafa object with a few interesting mask types:

svgMask – Luminosity+Alpha: Takes into account the color, alpha and shape of the mask shape to define the mask.

alpha – Uses the alpha of the mask shape to define the mask. This is equivalent to Flash Player native alpha masking

svgClip –  Uses the defined path of a shape of a mask shape to define the mask. Does not take into account things like strokes.

clip – this takes into account the filled region of the mask only to clip the maskee and is equivalent to the flash player native clipping mask

unMask – Removes any applied masks to show the mask fully rendered

You can see a simple example of Degrafa mask here. This feature will also be packaged as part of the Beta 3.2 release of Degrafa.