msgctl

msgctl 
id
, 
cmd
, 
arg

Calls the msgctl system call, which is used to perform different control operations on IPC message queues. See the msgctl documentation on your system for details. If cmd is &IPC_STAT , then arg must be a variable that will hold the returned msqid_ds structure. The return values work like those of fnctl : the undefined value for error, " 0 but true " for zero, or the actual return value otherwise. On error, it puts the error code into $! . Before calling, you should say:

require "ipc.ph";
require "msg.ph";

This function is available only on machines supporting System V IPC.