Net::DNS 0.66 is really old, released before January 2012. I can't find the sources for Net::DNS 0.66 at CPAN. Consider upgrading it to the most recent version.

As you can see from the script output, Net::DNS loads a lot of other modules, perhaps $SIG{CHLD} is deleted in one of the other modules. The following script should report where $SIG{CHLD} is modified. Run it on perl 5.12.1.

#!/usr/bin/perl

use v5.12;
use strict;
use warnings;

package SpyHash {

        use Tie::Hash; # for Tie::StdHash
        use Carp qw( carp );

        our @ISA=qw( Tie::StdHash );

        sub STORE
        {
                my ($self,$key,$value)=@_;
                $key=~/^CH?LD$/ and carp "Assign to key $key";
                return $self->SUPER::STORE($key,$value);
        }

        sub DELETE
        {
                my ($self,$key)=@_;
                $key=~/^CH?LD$/ and carp "Delete key $key";
                return $self->SUPER::DELETE($key);
        }

}

tie %SIG,'SpyHash';

$SIG{'CHLD'}=sub { 'just a dummy' }; # this line should be reported
require Net::DNS; # Any module messing with $SIG{'CHLD'} should be rep
+orted from here
Net::DNS->import(); # ... or here
[download]

Alexander

Hi there I had to modify the code you recommended I run because it was giving me the following error:

Invalid version format (non-numeric data) at perlmonkII.pl line 7, nea
+r "package SpyHash "
syntax error at perlmonkII.pl line 9, near "package SpyHash {
[download]

so I modified it to:

use v5.12;
use strict;
use warnings;

package SpyHash;

use Tie::Hash; # for Tie::StdHash
use Carp qw( carp );

our @ISA=qw( Tie::StdHash );

sub STORE{
        my ($self,$key,$value)=@_;
        $key=~/^CH?LD$/ and carp "Assign to key $key";
        return $self->SUPER::STORE($key,$value);
    }

sub DELETE
    {
        my ($self,$key)=@_;
        $key=~/^CH?LD$/ and carp "Delete key $key";
        return $self->SUPER::DELETE($key);
    }

   1;


package main;

tie %SIG,'SpyHash';

$SIG{'CHLD'}=sub { 'just a dummy' }; # this line should be reported
require Net::DNS; # Any module messing with $SIG{'CHLD'} should be rep
+orted from here
Net::DNS->import(); # ... or here
[download]

Then I ran this code on perl v.12.5 and I got

Assign to key CHLD at perlmonkII.pl line 34
[download]

I had to modify the code you recommended I run because it was giving me the following error:

Invalid version format (non-numeric data) at perlmonkII.pl line 7, nea
+r "package SpyHash "
syntax error at perlmonkII.pl line 9, near "package SpyHash {
[download]

Yepp, sorry, that's v5.14 syntax.

Then I ran this code on perl v.12.5 and I got

Assign to key CHLD at perlmonkII.pl line 34

So, it seems that Net::DNS does not modify $SIG{CHLD}. Or it does modify it so far behind the scenes that tie magic does not catch it.

Are you sure that your code does not mess with $SIG{CHLD}? Search all your sources for CHLD or $SIG.

Let's assume your code is clean. I added some calls to Data::Dumper to that code to verify the value of $SIG{CHLD}. Could you try that script? Comment out the tie %SIG,'SpyHash'; line and run again, so that we can see if tie has any effects.

#!/usr/bin/perl

use v5.12;
use strict;
use warnings;
use Data::Dumper;

package SpyHash;

use Tie::Hash; # for Tie::StdHash
use Carp qw( carp );

our @ISA=qw( Tie::StdHash );

sub STORE{
        my ($self,$key,$value)=@_;
        $key=~/^CH?LD$/ and carp "Assign to key $key";
        return $self->SUPER::STORE($key,$value);
    }

sub DELETE
    {
        my ($self,$key)=@_;
        $key=~/^CH?LD$/ and carp "Delete key $key";
        return $self->SUPER::DELETE($key);
    }

   1;


package main;

sub info
{
        my $where=shift;
        print $where,": ",Dumper($SIG{'CHLD'}),"\n";
}

info('start');
tie %SIG,'SpyHash';
info('after tie');
$SIG{'CHLD'}=sub { 'just a dummy' }; # this line should be reported
info('after set handler');
require Net::DNS; # Any module messing with $SIG{'CHLD'} should be rep
+orted from here
info('after require');
Net::DNS->import(); # ... or here
info('after import');
# For some extra paranoia, pretend to do some work with Net::DNS:
my $dns=Net::DNS::Resolver->new();
info('after creating instance');
my $reply=$dns->search('localhost');
info('after resolving localhost');
$reply=$dns->search('no.such.host.anywhere.invalid.');
info('after resolving junk');
[download]

Alexander

--
Today I will gladly share my knowledge and experience, for there are no sweeter words than "I told you so". ;-)