git: 9front

ref: e01d88046c40bb23331fb5bd45b9f27d61eb3fe5
dir: /sys/lib/man/permind/dup2.awk/

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$NF!=lastf2 {if(last2!="") print last2
	 lastf2=lastf1; last2=last1; lastf1=$NF; last1=$0}
$NF==lastf2 {print}
END {print last2; print last1}