variable definition

HI All, I am new to SPlunk. My colleague who is very experienced in this, had this in his code..

eval runtime="$run.value$"

I searched for the $run.value$ in the code and I couldn't find any. If anyone would please point me to where I can search for this , It will be of great relief. I am guessing this is some env variable, but I am not sure.

Thanks in advance… dak