dup mod sed

#!/bin/sed -f

# see http://theunixshell.blogspot.de/2014/05/inserting-lines-in-file-using-perl.html

# write line unchanged
p
# change to hold space
x
# initialize replacement sequence if it wasn't already
s/^$/5\"/
# append to original line
H
# cycle through numbers for next iteration
y/567/675/
# change to appended line
x
# remove old line end
s/.\"\n//