USV with 2 units by 2 records by 2 groups by 2 files:
a␟b␞c␟d␝e␟f␞g␟h␜i␟j␞k␟l␝m␟n␞o␟p
$ echo "a␟b␞c␟d␝e␟f␞g␟h␜i␟j␞k␟l␝m␟n␞o␟p" | sed 's/␟/,/g; s/␞/\n/g; s/␝/\n---\n/g; s/␜/\n===\n/g;' a,b c,d --- e,f g,h === i,j k,l --- m,n o,p