Labs Map Baker multiple frames

[spectronaut]

My bake is set up just right. Now I need to bake every frame. (I am baking a sim to a quad).... Switching Frames to Frame Range most definitely exports every frame but it overwrites the same file each time.
$F, $FRAME and $CURFRAME do nothing. 
Now it may be important to note, this Frame stepped bake process is handle in a script at the hda interface level. Unfortunatly I have not been able to glean anything. I really dont want to do this in a loop..

[spectronaut]

Turns out $F should have been ${F}