Library /sys$common/syshlp/mailhelp.hlb SPAWN, Qualifiers, /INPUT  *Conan The Librarian (sorry for the slow response - running on an old VAX)

       /INPUT=file-spec

    Specifies an input file containing one or more DCL command
    strings to be executed by the spawned subprocess. If you specify
    a command string along with an input file, the command string is
    processed before the commands in the input file. Once processing
    is complete, the subprocess is terminated.