src/cmd/index/range.sort - plan9 - Git at Google

 # range.sort
 #   Input/Output: string (tab) ["b"|"e"|"a"] (tab) number
 #   Sort by $1 (string), $3 (number), then $2 ("b"|"e"|"a")

 sort -u '-t	' +0 -1   +2n   +1 -2   $*
	# range.sort
	# Input/Output: string (tab) ["b"\|"e"\|"a"] (tab) number
	# Sort by $1 (string), $3 (number), then $2 ("b"\|"e"\|"a")

	sort -u '-t ' +0 -1 +2n +1 -2 $*