let proc p1 () ~
 let var c1: Char;
     proc p2 () ~
   let proc p3 () ~
    let proc p4 () ~
     let proc p5 () ~
      let proc p6 () ~
       let proc p7 () ~
        put (c1)
       in p7 ()
      in p6 ()
     in p5 ()
    in p4 ()
   in p3 ()
 in begin c1 := '+'; p2 () end
in p1 ()