INSTR(SEXP1,SEXP2) (INTEGER)

 Function
  Find the position of one string within another string.

 Syntax
  INSTR(str,sub)

   str = A string expression to look for sub in.
   sub = A string expression to search for.

 Return Type & Value
  INTEGER
  Returns the 1-based position of sub within str or 0 if sub is not
  found within str. (1-based means the first character of str is position 1)

 Remarks
  This function is useful for determining if a particular word or phrase
  exists in a string.  The return value is the position of the sub string
  within the longer string.  The first character of str is position 1, the
  second is position 2, and so on.  If sub is not found in str, 0 is returned.

 Examples
  STRING s
  WHILE (INSTR(UPPER(s),"QUIT") = 0) DO
    INPUTTEXT "Enter string",s,@X0E,40
    NEWLINE
    PRINTLN s
  ENDWHILE