1h 2 3:b 4# On the last line, print and exit 5$b 6N 7/^\(.*\)\n\1$/ { 8 # The two lines are identical. Undo the effect of 9 # the n command. 10 g 11 bb 12} 13 14# If the @code{N} command had added the last line, print and exit 15$b 16 17# The lines are different; print the first and go 18# back working on the second. 19P 20D 21