You are viewing the version of this documentation from Perl blead. This is the main development branch of Perl. (git commit 201ee5d599737a9c43a8681dbf23e0cb4658be60)
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.