You are viewing the version of this documentation from Perl blead. This is the main development branch of Perl. (git commit 909c414e5450fe64ba145e6a3f3ed2e97999f060)
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.