--- a/plugins/check_dns-serial	Tue Dec 30 12:24:43 2014 +0100
+++ b/plugins/check_dns-serial	Tue Dec 30 14:40:45 2014 +0100
@@ -44,8 +44,8 @@
 use Getopt::Long qw(GetOptionsFromArray);
 use Net::DNS;
 use Pod::Usage;
+use Smart::Comments;
 
-my %resolver;
 sub uniq { my %h; @h{@_} = (); return keys %h; }
 
 # return a list of the zones known to the local
@@ -94,26 +94,30 @@
 }
 
 # return a list of "official" nameservers
-sub get_ns {
-    my ($nameserver) = map { /^\@(.*)/ } $_[0] =~ /^\@/ ? shift : '@8.8.8.8';
-    my ($domain) = @_;
+sub ns {
+    my $domain = shift;
+    ### assert: @_ % 2 == 0
+    my %resflags = (nameservers => [qw/8.8.8.8/], @_);
+    my $aa = delete $resflags{aa};
+    my $nameservers = $resflags{nameservers};
     my @ns;
 
-    my $r = $resolver{$nameserver} //=
-      Net::DNS::Resolver->new(nameservers => [$nameserver]);
-    my $q = $r->query($domain, 'NS') or die $r->errorstring, "\@$nameserver\n";
+    my $r = Net::DNS::Resolver->new(%resflags);
+    my $q = $r->query($domain, 'NS') or die $r->errorstring, "\@@$nameservers\n";
+
+    die "no aa @@$nameservers\n" if $aa and not $q->header->aa;
     push @ns, map { $_->nsdname } grep { $_->type eq 'NS' } $q->answer;
 
     return sort @ns;
 }
 
-sub get_serial {
-    my ($nameserver) = map { /^\@(.*)/ } $_[0] =~ /^\@/ ? shift : '@8.8.8.8';
-    my ($domain) = shift;
+sub serial {
+    my $domain = shift;
+    my %resflags = (nameservers => [qw/8.8.8.8/], @_);
+    my $nameservers = $resflags{nameservers};
 
-    my $r = $resolver{$nameserver} //=
-      Net::DNS::Resolver->new(nameservers => [$nameserver]);
-    my $q = $r->query($domain, 'SOA') or die $r->errorstring, "\@$nameserver\n";
+    my $r = Net::DNS::Resolver->new(%resflags);
+    my $q = $r->query($domain, 'SOA') or die $r->errorstring, "\@@$nameservers\n";
     return (map { $_->serial } grep { $_->type eq 'SOA' } $q->answer)[0];
 }
 
@@ -127,10 +131,10 @@
 # CRITICAL - if the serial cannot be found at one of the sources
 
 sub ns_ok {
-    my ($reference, $domain) = @_;
+    my ($domain, $reference) = @_;
 
-    my @our = sort eval { get_ns($reference, $domain) };
-    my @their = sort +get_ns($domain);
+    my @our = sort +ns($domain, nameservers => [$reference], aa => 1);
+    my @their = sort +ns($domain);
 
     {
         local $" = "\0";
@@ -148,8 +152,6 @@
 
     GetOptionsFromArray(
         \@argv,
-## Please see file perltidy.ERR
-## Please see file perltidy.ERR
         'reference=s' => \$opt_reference,
         'progress!'   => \$opt_progress,
         'h|help'      => sub { pod2usage(-verbose => 1, -exit => 0) },
@@ -168,7 +170,7 @@
     my (@OK, %CRITICAL);
     foreach my $domain (@domains) {
         print STDERR "$domain " if $opt_progress;
-        eval { ns_ok('@212.80.235.130', $domain) };
+        eval { ns_ok($domain, $opt_reference) };
         if ($@) { $CRITICAL{$domain} = $@ }
         else    { push @OK, $domain }
         say STDERR $@ ? 'not ok' : 'ok' if $opt_progress;