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

 command-string

    Specifies a command string of less than 132 characters that is
    to be executed in the context of the created subprocess. When
    the command completes execution, the subprocess terminates and
    control returns to the parent process. If both a command string
    and the /INPUT qualifier are specified, the specified command
    string executes before additional commands are obtained from the
    /INPUT qualifier.