The SOR$PASS_FILES routine passes input and output file
    specifications to SORT. The SOR$PASS_FILES routine must be
    repeated for multiple input files. The output file name string
    and characteristics should be specified only in the first call to
    SOR$PASS_FILES.

    This routine also accepts optional arguments that specify
    characteristics for the output file. By default, the output file
    characteristics are the same as the first input file; specified
    output file characteristics are used to change these defaults.

    Some of the following condition values are used with different
    severities, depending on whether SORT/MERGE can recover. Thus,
    if you want to check for a specific status, you should use
    LIB$MATCH_COND.