You are viewing the version of this documentation from Perl blead. This is the main development branch of Perl. (git commit 94b79ff119f82f12ab36be7c30e77d9e5f51c0bd)
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.