You are viewing the version of this documentation from Perl blead. This is the main development branch of Perl. (git commit 06c43a51065a7d4d3f3ed53aebe5439dc28f839c)
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.