You are viewing the version of this documentation from Perl blead. This is the main development branch of Perl. (git commit 0a05a8bd231063e1ba6d039754d9e635d47441b5)
listen SOCKET,QUEUESIZE

Does the same thing that the listen(2) system call does. Returns true if it succeeded, false otherwise. See the example in "Sockets: Client/Server Communication" in perlipc.