I suppose that depends on whether the pairs have to pulled from the list in the same order in which they appear in the list ... which altho' implied, isn't, AFAICT, specified in/by the OP.
Ooops, my mistake, it _is_ specified : 'This array should be processed left-to-right...'
A user level that continues to overstate my experience :-))
Comment on Re^3: Processing pairs of values from even-sized array