%RxFind("text some text", "[a-z]+", 1) ;returns the value of 1
%RxFind("123text some text", "[a-z]+", 1) ;returns the value of 4
%RxFind("text some text", "[a-z]+", 5, _first, _last) ;returns the value of 6, _first = 6, _last = 11
%RxFind("text some text", "[a-z]+", 20, _first, _last) ;returns the value of -1, _first = -1, _last = -1
%RxFind("text some text", "", 20, _first, _last) ;returns undefined value (length of regexp is 0), _first = 0, _last = 0