It was not a mel to make smoke trails, it was a mel called "DetachSeparate" to better help "destroy" polygon object(s).
In the much larger video tutorial series, Dynamic Explosions 2,
I walk you through a way to make your own smoketrail/fire shader(s).
Am I wrong?
I'll check.....
Israel "Izzy" Long
Motion and Title Design for Broadcast-Film-DS
izzylong.com