The following example is from the bootstrap global PCL
sys.dbg.set().
This PCL is called from any bootstrap program when the
user12 key is pressed.
if (sys.uscr_dbflag == "ON")
sys.uscr_dbflag = "OFF";
else
sys.uscr_dbflag = "ON";
sys.set_debug(sys.uscr_dbflag);