in reply to Check network MTU size
If you're creating raw packets in Perl, have a look at Net::Frame modules and Net::Pcap.
If you're on Windows, Net::Pcap has some issues. See Re: Net::Pcap installation help (and not with the library)
Finally, I've put a nice shell (think 'scapy') over the Net::Frame / Net::Pcap modules - Perl Packet Crafter (PPC). You can find it here:
http://www.vinsworld.com/software/ppc.htmlhttp://www.vinsworld.com/software/ppc.zip
In Section
Cool Uses for Perl