log info line yada yada 1
log info line yada yada 2
log info line yada yada 3
log info line (pattern) 4
log info line yada yada 5
...

##</code><code>##

log info line yada yada 1
log info line yada yada 2
log info line yada yada 3
(pattern) (Put line number here, or some type of result mark)
...

##</code><code>##

open(INFILE, "< file.log")
     	or die "Cant open file : $!";

open(OUT, "> results.txt")
     	or die "Cant open new file : $!";

$pattern = "Error code 2";
	while (<INFILE>) {

	$a[$i++%3] = $_;
	print OUT $a[$i%3]
	if /$pattern/;
}

close INFILE;
close OUT;