perlfun_socketpair.txt

    socketpair SOCKET1,SOCKET2,DOMAIN,TYPE,PROTOCOL
            Creates an unnamed pair of sockets in the specified domain, of
            the specified type. DOMAIN, TYPE, and PROTOCOL are specified the
            same as for the syscall of the same name. If unimplemented,
            raises an exception. Returns true if successful.

            On systems that support a close-on-exec flag on files, the flag
            will be set for the newly opened file descriptors, as determined
            by the value of $^F. See "$^F" in perlvar.

            Some systems define "pipe" in terms of "socketpair", in which a
            call to "pipe($rdr, $wtr)" is essentially:

                use Socket;
                socketpair(my $rdr, my $wtr, AF_UNIX, SOCK_STREAM, PF_UNSPEC);
                shutdown($rdr, 1);        # no more writing for reader
                shutdown($wtr, 0);        # no more reading for writer

            See perlipc for an example of socketpair use. Perl 5.8 and later
            will emulate socketpair using IP sockets to localhost if your
            system implements sockets but not socketpair.

            Portability issues: "socketpair" in perlport.