Procedure.i reduce(List l(),op$="+")
  If FirstElement(l())
    x=l()
    While NextElement(l())
      Select op$
        Case "+" : x+l()
        Case "-" : x-l()
        Case "*" : x*l()
      EndSelect
    Wend
  EndIf
  ProcedureReturn x
EndProcedure

NewList fold()
For i=1 To 5 : AddElement(fold()) : fold()=i : Next

Debug reduce(fold())
Debug reduce(fold(),"-")
Debug reduce(fold(),"*")