Pathes starting with '+', what is it??

[Adam Vodopjan]

In corecmd.c I see such code:

 81   if (argv[0][0] == '/' || argv[0][0] == '(' || argv[0][0] == '+')
 82     mod = grub_dl_load_file (argv[0]);
 83   else
 84     mod = grub_dl_load (argv[0]);


What are those pathes started with '+' ??