A very interesting DSL for network packet manipulation is Scapy(http://www.secdev.org/projects/scapy/).

It uses python itself as a DSL to make things like packet forging easy:

  >>> Ether()/IP()/TCP()/"GET / HTTP/1.0\r\n\r\n"
  <Ether type=0x800 |IP frag=0 proto=TCP |<TCP |<Raw load='GET / HTTP/1.0\r\n\r\n' |>>>>

Here the / operator was overloaded to stack layers.