Perspective needs a unit to work with firefox.

[chriseppstein]

PR #1703 had a fix for the old system.

[jamierytlewski]

Maybe I'm off on this, but it seems as though the documentation just needs to be fixed on this page. http://compass-style.org/reference/compass/css3/transform/#mixin-perspective instead of unitless, could it say px or should the code be changed to a 'px' if 'px' does not exist. If I use the code:

@include perspective(500px);

I get the proper output. using 1.0.1 of Compass.