7z Command Line Syntax essentially preserves some kind of standard syntax key of Backus-Naur form:
Notation Description Text without brackets or braces Items you must type as shown <Text inside angle brackets> Placeholder for which you must supply a value [Text inside square brackets] Optional items Set of required items; choose one Vertical bar (|) Separator for mutually exclusive items; choose one Ellipsis (…) Items that can be repeated
As neither @ nor ! is enclosed in any brackets or braces, you need to use them literally:
@: Specifies name of list file. See List file description!: Specifies wildcard or filename
Example:
-i@c:\temp\abc.txtmeans include all files matching criteria listed in thec:\temp\abc.txtfile-i!c:\temp\abc.txtmeans include the filec:\temp\abc.txtitself.