/sys$common/syshlp/helplib.hlb @, Parameters  *Conan The Librarian (sorry for the slow response - running on an old VAX)

 filespec

    Specifies either the input device or the file for the preceding
    command, or the command procedure to be executed. The default
    file type is .COM. The asterisk (*)  and the percent sign (%)
    wildcard characters are not allowed in the file specification.

 parameter[,...]

    Specifies from one to eight optional parameters to pass to the
    command procedure. The symbols (P1, P2, . . . P8) are assigned
    character string values in the order of entry. The symbols are
    local to the specified command procedure. Separate each parameter
    with one or more blanks. Use two consecutive quotation marks
    ("")  to specify a null parameter. You can specify a parameter
    with a character string value containing alphanumeric or special
    characters, with the following restrictions:

    o  The command interpreter converts alphabetic characters to
       uppercase and uses blanks to delimit each parameter. To pass a
       parameter that contains embedded blanks or literal lowercase
       letters, place the parameter in quotation marks.

    o  If the first parameter begins with a slash (/),  you must
       enclose the parameter in quotation marks (" ").

    o  To pass a parameter that contains literal quotation marks
       and spaces, enclose the entire string in quotation marks and
       use two consecutive quotation marks within the string. For
       example, the command procedure TEST.COM contains the following
       line:

       $ WRITE SYS$OUTPUT P1

       Enter the following at the DCL prompt ($):

       $ @TEST "Never say ""quit"""

       When the procedure TEST.COM executes, the parameter P1 is
       equated to the following string:

       Never say "quit"

       If a string contains quotation marks and does not contain
       spaces, the quotation marks are preserved in the string and
       the letters within the quotation marks remain in lowercase.
       For example, enter the following at the DCL prompt:

       $ @TEST abc"def"ghi

       When the procedure TEST.COM executes, the parameter P1 is
       equated to the following string:

       ABC"def"GHI

    To use a symbol as a parameter, enclose the symbol in single
    quotation marks (` ')  to force symbol substitution. For example:

    $ NAME = "JOHNSON"
    $ @INFO 'NAME'

    The single quotation marks cause the value "JOHNSON" to be
    substituted for the symbol NAME. Therefore, the parameter
    "JOHNSON" is passed as P1 to INFO.COM.