At initialisation
     Contents are 1 2
In assignTo - assign to @_
     Contents now 1 2
In listArgs - list of lexicals
     Contents now 1 2
In loopOver - loop over @_
     Contents now 2 3
In refTo - take reference to @_ elements
     Contents now 3 4
In shiftArgs - lexicals via shift
     Contents now 3 4
In useDirect - increment elements directly
     Contents now 4 5