Net-RawIp version is: Net-RawIp-0.25.  
Linux machine OS is:
[root@auto-12 tools]# uname -a
Linux auto-12 2.6.18-92.el5 #1 SMP Tue Jun 10 18:49:47 EDT 2008 i686 i686 i386 GNU/Linux  

The command is as follows:
[root@auto-12 examples]# ./land --src=50.254.1.12 --srcport=1032 --srcmac=00:1B:21:01:F1:8D --dest=50.100.1.3 --destport=1033 --type=tcp --number=3000 --srceth=eth0 constructing tcp packets
(tap) Can't get interface IP address at /usr/lib/perl5/site_perl/5.8.8/i386-linux-thread-multi/Net/RawIP.pm line 223.

The perl script part is:
$packet->ethnew(eth0);  <=================================complain
if ($arg_src_mac) {
        $packet->ethset(source=>$arg_src_mac);
}
if ($arg_dest_mac) {
        $packet->ethset(dest=>$arg_dest_mac);
}

Any idea why the tap function of eth.c is not working?
Thanks