Perl5 リファレンス

               Opens a socket of the specified kind and attaches
               it to filehandle SOCKET.  DOMAIN, TYPE, and
               PROTOCOL are specified the same as for the system
               call of the same name.  You should `use Socket'
               first to get the proper definitions imported.  See
               the examples in the Sockets: Client/Server
               Communication entry in the perlipc manpage.

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