#!/usr/bin/env perl
use warnings;
use strict;

my @files = glob '/path/*.log';
my $out_filename = 'output.txt';

open my $out_fh, '>', $out_filename
	or die "open $out_filename: $!";
for my $filename (@files) {
	next if $filename =~ /regex to exclude undesired filenames/;
	open my $fh, '<', $filename
		or die "open $filename: $!";
	while (<$fh>) {
		next unless /regex to match desired lines/;
		print {$out_fh} $_;
	}
	close $fh;
}
close $out_fh;

##</code><code>##

$ ls /path/*.log | grep -v filename_exclude_pat
  | xargs grep -h line_include_pat >output.txt