use strict;
use warnings;

my ( %named_conf, @unlistedFiles );

open my $fh, '<', 'named.conf' or die $!;
/\s+file\s+"([^"]+)/ and $named_conf{$1}++ for <$fh>;
close $fh;

chdir 'zonefiles' or die $!;
!defined $named_conf{$_} and push @unlistedFiles, $_ for <db.*>;

print "$_\n" for @unlistedFiles;

##</code><code>##

db.127.0.0
db.brian.com
db.cache
db.test.com
db.what
db.why

##</code><code>##

db.what
db.why