Hi there,

Thanks for your suggestion (I think I already mentioned the OS in my first post but here it is again: Red Hat Enterprise Linux Server release 5.11; also perl -v says my perl was built for built for x86_64-linux-thread-multi)- I ran your script and here is the output I get:

perl v5.8.8
---------------

start: $VAR1 = undef;

after set handler: $VAR1 = sub { "DUMMY" };

after require: $VAR1 = sub { "DUMMY" };

after import: $VAR1 = sub { "DUMMY" };


OS: linux
Versions:
Perl
Carp 1.04
Config none
Data::Dumper 2.121_08
Errno 1.0901
Exporter 5.58
Exporter::Heavy 5.58
IO 1.22
IO::Handle 1.25
IO::Select 1.17
IO::Socket 1.29
IO::Socket::INET 1.29
IO::Socket::UNIX 1.22
Net::DNS 0.66
Net::DNS::Header 704
Net::DNS::Packet 837
Net::DNS::Question 800
Net::DNS::RR 828
Net::DNS::RR::Unknown 388
Net::DNS::Resolver 830
Net::DNS::Resolver::Base 830
Net::DNS::Resolver::UNIX 482
Net::DNS::Update 517
SelectSaver 1.01
Socket 1.78
Symbol 1.06
XSLoader 0.06
bytes 1.02
constant 1.05
overload 1.04
strict 1.03
vars 1.01
warnings 1.05
warnings::register 1.01
[download]

perl v 5.12.5
-----------------

start: $VAR1 = undef;

after set handler: $VAR1 = sub { "DUMMY" };

after require: $VAR1 = undef;

after import: $VAR1 = undef;


OS: linux
Versions:
Perl v5.12.5
Carp 1.17
Config none
Data::Dumper 2.131
Errno 1.11
Exporter 5.64_01
Exporter::Heavy 5.64_01
IO 1.25_02
IO::Handle 1.28
IO::Select 1.17
IO::Socket 1.31
IO::Socket::INET 1.31
IO::Socket::UNIX 1.23
Net::DNS 0.66
Net::DNS::Header 704
Net::DNS::Packet 837
Net::DNS::Question 800
Net::DNS::RR 828
Net::DNS::RR::Unknown 388
Net::DNS::Resolver 830
Net::DNS::Resolver::Base 830
Net::DNS::Resolver::UNIX 482
Net::DNS::Update 517
SelectSaver 1.02
Socket 1.87_01
Symbol 1.07
XSLoader 0.15
bytes 1.04
constant 1.20
overload 1.10
strict 1.04
vars 1.01
warnings 1.09
warnings::register 1.01
[download]

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

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

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]