VERIFY (string, set [,back] [,kind])

  Class:  Elemental function - Generic

  Verifies that a set of characters contains all the characters in a
  string by identifying the first character in the string that is not
  in the set.

  The "set" must be of type character with the same kind type
  parameter as "string".  The "back" must be of type logical.  The
  "kind" must be a scalar integer initialization expression.

  The result is of type integer.  If "kind" is present, the kind
  parameter of the result is that specified by "kind"; otherwise, the
  kind parameter of the result is that of default integer.  If the
  processor cannot represent the result value in the kind of the
  result, the result is undefined.

  If "back" is absent (or is present with the value false) and
  "string" has at least one character that is not in "set", the value
  of the result is the position of the leftmost character of "string"
  that is not in "set".

  If "back" is present with the value true and "string" has at least
  one character that is not in "set", the value of the result is the
  position of the rightmost character of "string" that is not in
  "set".

  If each character of "string" is in "set" or the length of "string"
  is zero, the value of the result is zero.

  Examples:

  VERIFY ('CDDDC', 'C') has the value 2.

  VERIFY ('CDDDC', 'C', BACK=.TRUE.) has the value 4.

  VERIFY ('CDDDC', 'CD') has the value zero.