...
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 der Loop: $s_count bearbeite device: $akt_dev\n";
    my $error = Net::Pcap::loop( $object1, 1, \&callback, [ $netaddr1, $netmask1 ] );
    print "dahinter - $error <\n";
  }
}
...