perl -slnE "BEGIN{$r=qr/$r/;push @ARGV,$ARGV[0]}eof&&!$y?$y=close ARGV:/$r&&!$y?push@u,$.-$n..$.+$n:$y&&!($.~~@u)?say:0" -- -r=XXXXX -n=1 next-and-previous.txt 11111 22222 33333 44444