Availability:C-language interface function
(return) foreign_t PL_retry(intptr_t 
value)The foreign function succeeds while leaving a choice point. On 
backtracking over this goal the foreign function will be called again, 
but the control argument now indicates it is a‘Redo’call and 
the macro PL_foreign_context() 
returns the handle passed via
PL_retry(). 
This handle is a signed value two bits smaller than a pointer, i.e., 30 
or 62 bits (two bits are used for status indication). Defined as return 
_PL_retry(n). 
See also PL_succeed().