It concludes by implementing a fold:

   define
   {
       [Fold]<- {
           rearrange
           {
               rearrange
               {
                   dequote
                   choose
                   quote Result
                   pair pair pair {[Fold]<-} Function Result Remainder
                   Remainder
               }
               {Result Remainder}
               dequote Function Base <-[terms] Source
           }
           {Function Base Source}
        }
   }
   {
       [Fold]<- {[literal]<-} {} {1 2 3}
   }