There is no perl module named Net::BGP4, there is however a module Net::BGP, which seems the same as the content of the port net/p5-Net-BGP4. The port should be renamed and have the patch below applied. How-To-Repeat: search.cpan.org
Responsible Changed From-To: freebsd-ports->skv over to maintainer
State Changed From-To: open->closed Fixed, thanks.