...
$SIG{__DIE__} = \&dieerr;
$SIG{__WARN__} = \&warnerr;

sub warnerr{
my $msg = shift;
print $msg;
}

sub dieerr{
my $msg = shift;
print $msg;
}

my $s_count=0;
while(1) {
  $s_count++;
  foreach my $akt_dev (keys %h_dev) {
    my $object1  = $h_dev{$akt_dev}{"object"};
    my $netaddr1 = $h_dev{$akt_dev}{"netaddr"};
    my $netmask1 = $h_dev{$akt_dev}{"netmask"};

    print "\nvor Net::Pcap:loop: $s_count bearbeite device: $akt_dev --";
    my $error = Net::Pcap::loop( $object1, 1, \&callback, [ $netaddr1, $netmask1 ] )||warn ("Fehler: > $! <");
    print "dahinter > $error <\n";
  }
}