In response to this question on using a conditional to define a TikZ style it was suggested to use /utils/exec.
It is easy to find uses of this, but I have not been able to locate documentation on it. I have looked in the TeXbook and TeX By Topic, but did not find this.
So, where what exactly is /utils/exec and where can I find documentation on it. Under what conditions should one use this or not use this?
pgfmanual. You wont find such things in the TeXBook or in TeX By Topic, they list only plainTeX macros but not (La)TeX packages. – Martin Scharrer♦ May 10 '11 at 7:28