Where is *brbk defined as comma char??

In the program ArduPilot_EasyStar_V22 there is a declaration:

char *brkb, *pEnd;

In GPS_NEMA.pde, there is a statement:

token = strtok_r(gps_buffer, search, &brkb);

where the string is parsed by looking for the data between commas.

Where is &brkb defined as the comma character. I can't find it in the program files or headers?

It is not! search is defined as ",".

I cannot believe I asked this question. Thanks for pointing out what should have been obvious to me...