x=1 y=2
[ "$(
	case $((x+=1)) in
	($((y+=1)))	echo bad1 ;;
	($((y-1)))	echo $x.$y ;;
	($((y=2)))	echo bad2 ;;
	(*)		echo bad3 ;;
	esac
)" = "2.3" ] || echo "Error at $LINENO"
[ "$x.$y" = "1.2" ] || echo "Error at $LINENO"