See the current Perl documentation for msgrcv.

Here is our local, out-dated (pre-5.6) version:

msgrcv - receive a SysV IPC message from a message queue


Calls the System V IPC function msgrcv to receive a message from message queue ID into variable VAR with a maximum message size of SIZE. Note that if a message is received, the message type will be the first thing in VAR, and the maximum length of VAR is SIZE plus the size of the message type. Returns TRUE if successful, or FALSE if there is an error. See also IPC::SysV and IPC::SysV::Msg documentation.