--with

All arguments after --with are passed in for rule use

@prefix log: <http://www.w3.org/2000/10/swap/log#> .
@prefix string: <http://www.w3.org/2000/10/swap/string#>.
@prefix os: <http://www.w3.org/2000/10/swap/os#>.

{ "2" os:argv ?x.
} => {
   ""  log:outputString ?x.
}.

cwm os-rule.n3 --think --strings --with foo bar baz outputs bar (with no final newline).