Quote

send SOCKET,MSG,FLAGS,TO
send SOCKET,MSG,FLAGS
Sends a message on a socket. Attempts to send the scalar MSG to the SOCKET filehandle. Takes the same flags as the system call of the same name. On unconnected sockets, you must specify a destination to send to, in which case it does a sendto(2) syscall. Returns the number of characters sent, or the undefined value on error. The sendmsg(2) syscall is currently unimplemented. See "UDP: Message Passing" in perlipc for examples.

Note the characters: depending on the status of the socket, either (8-bit) bytes or characters are sent. By default all sockets operate on bytes, but for example if the socket has been changed using binmode to operate with the :encoding(UTF-8) I/O layer (see open, or the open pragma), the I/O will operate on UTF-8 encoded Unicode characters, not bytes. Similarly for the :encoding layer: in that case pretty much any characters can be sent.