In my case the same error 'send: Cannot determine peer address' arised, but it is because when program A is trying to send(IO::socket) data on socket (program B is connected to the other end) and the program B has just exited abnormally.
I have already trapped the PIPE signal in program A, but in this case I am not even receiving PIPE signal,(thinking that I am using write).
Later while seeing this IO::Socket::send, i found that when that error is croaked, the write even is not attempted, so I just checked whether the peer is defined or not, before calling IO::Socket::send.
I presume in other cases(such as plain write) we may receive SIGPIPE.