The Find First Character That Does Not Occur in Set routine
    searches a string, comparing each character to the characters in
    a specified set of characters. The string is searched character
    by character, from left to right. STR$FIND_FIRST_NOT_IN_SET
    returns the position of the first character in the string that
    does not match any of the characters in the selected set of
    characters.

    Format

      STR$FIND_FIRST_NOT_IN_SET  source-string ,set-of-characters

1  –  Returns

    OpenVMS usage:longword_signed
    type:         longword (signed)
    access:       write only
    mechanism:    by value

    Position in source-string where a nonmatch was found.

    On Alpha systems, if the relative position of the substring can
    exceed 2**32-1, assign the return value to a quadword to ensure
    that you retrieve the correct relative position.

    Returned
    Value         Condition

    0             Either all characters in source-string match some
                  characters in set-of-characters, or there were no
                  characters in set-of-characters.
    1             Either the first nonmatching character in source-
                  string was found in position 1, or there were no
                  characters in source-string.
    N             The first nonmatching character was found in
                  position N within source-string.

2  –  Arguments

 source-string

    OpenVMS usage:char_string
    type:         character string
    access:       read only
    mechanism:    by descriptor

    String that STR$FIND_FIRST_NOT_IN_SET searches. The source-string
    argument is the address of a descriptor pointing to the string.

 set-of-characters

    OpenVMS usage:char_string
    type:         character string
    access:       read only
    mechanism:    by descriptor

    The set of characters that STR$FIND_FIRST_NOT_IN_SET compares
    to the string, looking for a nonmatch. The set-of-characters
    argument is the address of a descriptor pointing to this set of
    characters.