Missing shading global variable 'L'

[R_cyph]

I'm trying to access this global variable "L" but it seems to be missing from the globals in a material builder in the /mat context. If I use a parameter node to call L it errors out saying there is already a global variable L. 

 

from the docs:

L (read-only)

Vector from the point on the surface to the light source. The length of this vector represents the distance to the light source.

[R_cyph]

Apparently, you can only see it in an illuminance loop vop.