program substitution;
    template := [[[1,2],[3,4,1],5]];
    payload := {
        [0,"Payload#0"], [1,"Payload#1"], [2,"Payload#2"], [3,"Payload#3"],
        [4,"Payload#4"], [5,"Payload#5"], [6,"Payload#6"]
    };

    print(subst(template, payload));

    proc subst(template, payload);
        if not is_tuple(template) then
            return(payload(template));
        end if;

        result := [];
        loop for item in template do
            result with:= subst(item, payload);
        end loop;
        return result;
    end proc;
end program;