Library /sys$common/syshlp/basichelp.hlb INSTR, Syntax  *Conan The Librarian (sorry for the slow response - running on an old VAX)

      int-var = INSTR(int-exp, str-exp1, str-exp2)

  The search begins at the location specified by int-exp, looking for  the
  first occurrence of str-exp2 in str-exp1.