Here is a version that I based heavily on jeffa's version above.

use strict;
use warnings;
use Tie::File;
use Getopt::Std;

our %opts;
getopt('AB',\%opts);
die "USAGE: $0 [-An] [-Bn] match file" unless @ARGV;
my ($match,$filename) = @ARGV;

my @file;
tie @file, 'Tie::File', $filename, autochomp => 0;

my @prebuffer;
my $postbuffer_counter = 0;
foreach (@file) {
  if (/$match/) {
    print @prebuffer, $_;
    @prebuffer = ();
    $postbuffer_counter = $opts{A} || 0;
  } else {
    if ($postbuffer_counter-- > 0) {
      print $_
    } else {
      push @prebuffer, $_;
      shift @prebuffer if @prebuffer > $opts{B};
    }
  }
}

[download]

This prints as it finds matches and handles matches that are close together. I haven't done a whole lot of testing, so there very well may be other issues.

Comments and suggestions are welcome...

Cees

In reply to Re: linux grep feature by cees
in thread Emulating GNU grep -A and -B switches with perl (was: linux grep feature) by perlisfun

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