Sehr wahrscheinlich hier ???  -->>  open (IFCONFIG, "$ifconfig $ethif 2>&1 |") || die ("ERROR (gen2nfs_sub_ifconfig_ipv4): $! $_");

sub gen2nfs_sub_ifconfig_mac {

                my $ethif = shift;
                my $ifconfig = "$IFCONFIG";
                my $string = 'HWaddr';
                local *IFCONFIG;

                open (IFCONFIG, "$ifconfig $ethif 2>&1 |") || die ("ERROR (gen2nfs_sub_ifconfig_mac): $! $_");

                while(<IFCONFIG>) {

                        # search MAC 00:00:00:00:00:00
                        #            ww:ww:ww:ww:ww:ww
                        # \w = word

                        if ( /^.*$string\s(\w\w:\w\w:\w\w:\w\w:\w\w:\w\w)/ ) {
                                return "$1";
                                last;
                        } else {
                                die ("ERROR (gen2nfs_sub_ifconfig_mac): $! $_" );
                        };
                }

                close (IFCONFIG);
}