A little bit more code than needed, and some information missing.

What OS do you use? Which version? Module versions could also be interesting. I suggest to run the following script (use the download link) with both Perl versions and to post its output, wrapped in <code> tags:

#!/usr/bin/perl

use strict;
use warnings;
use Data::Dumper;

$Data::Dumper::Sortkeys=1;

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

info('start');
$SIG{'CHLD'}=sub { 'oh well, just a dummy' };
info('after set handler');
require Net::DNS;
info('after require');
Net::DNS->import();
info('after import');

print "\n";

print "OS: $^O\n";

print "Versions:\n";
print "Perl $^V\n";
for my $fn (sort keys %INC) {
        my $mod=$fn;
        $mod=~s|/|::|g;
        $mod=~s|\.pm$|| or next;
        my $ver=do {
                no strict 'refs';
                defined ${"$mod\::VERSION"} ? ${"$mod\::VERSION"} : 'n
+one'
        };
        print "$mod $ver\n";
}
[download]

The first lines up to print "\n" are the real test code, everything following that collects information (OS, Perl version, Module versions).

Alexander