incrementing integers in sed

#!/bin/sed -f
#Increment integers. Handles multiple numbers per line.

#bracket numbers with < >
s/[0-9]\+/<&>/g

#tail lines with how many times to increment, less one.
#set addresses here to get multiple increments on selected lines
/[0-9]\+/s/.*/& IIII/

#start of increment loop
:a

# replace all trailing 9s by _
:d
s/9\(_*\)>/_\1>/
td

# incr last digit only.  The last line adds a most-significant
# digit of 1 if we have to add a digit.
s/8\(_*\)>/9\1>/g
s/7\(_*\)>/8\1>/g
s/6\(_*\)>/7\1>/g
s/5\(_*\)>/6\1>/g
s/4\(_*\)>/5\1>/g
s/3\(_*\)>/4\1>/g
s/2\(_*\)>/3\1>/g
s/1\(_*\)>/2\1>/g
s/0\(_*\)>/1\1>/g
s/<\(_*\)>/<1\1>/g

#/[<0-8]_*>/s/.*/NumLine & numline/g

#replace _ with 0
y/_/0/

#end of increment loop
#first, an empty loop to 'flush' status
tb;:b
#remove one 'I' from the tail, and loop until none left
s/ \(I*\)I$/ \1/; ta

#remove < > bracketing
s/<\([0-9]\+\)>/\1/g