See the current Perl documentation for msgget.
Here is our local, out-dated (pre-5.6) version:

msgget - get SysV IPC message queue

msgget KEY,FLAGS

Calls the System
V
IPC function
msgget(2). Returns the message queue id, or the undefined value if there is an error. See also
IPC::SysV
and IPC::SysV::Msg documentation.