VMS Help MACRO, VAX MACRO Assembler, Parameter  *Conan The Librarian (sorry for the slow response - running on an old VAX)

 filespec[,...]

    Specifies a VAX MACRO assembly language source file to be
    assembled. If you specify more than one file, separate the file
    specifications with either commas (,) or plus signs (+).  File
    specifications separated by commas cause the MACRO assembler to
    produce an object file (and, if indicated, a listing file) for each
    specified file. File specifications separated by plus signs are
    concatenated into one input file and produce a single object file
    (and listing file).

    You cannot include  the asterisk (*) and the percent sign (%)
    wildcard characters in a file specification. For each file
    specification, the MACRO command supplies a default file type .MAR.
    The MACRO assembler creates output files of one version higher than
    the highest version existing in the target directory.