OpenVMS usage:longword_unsigned
    type:         longword (unsigned)
    access:       write only
    mechanism:    by value

    The values returned by STR$FIND_FIRST_SUBSTRING and the
    conditions to which they translate are as follows:

    Returned
    Value          Condition

    0              source-string did not contain any of the specified
                   substrings.
    1              STR$FIND_FIRST_SUBSTRING found at least one of the
                   specified substrings in source-string.