/sys$common/syshlp/helplib.hlb FORTRAN, Built-in Functions, %REF  *Conan The Librarian (sorry for the slow response - running on an old VAX)

  %REF (arg)
  Forces an actual argument in a CALL statement or function reference
  to be passed by reference:  the address of the argument is passed
  to the subprogram.  By default, Fortran passes all numeric values
  by reference.