You are viewing the version of this documentation from Perl blead. This is the main development branch of Perl. (git commit 8e50dbf32b80ca84a9d4d8c9d63010c54aa73018)
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.