This function calls the msgctl(2) system call.
See msgctl(2) for details.
ARG must be a
variable that will hold the returned
msqid_ds structure. The
return value works like ioctl's: 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
require "ipc.ph"; require "msg.ph";
This function is available only on machines supporting System V IPC, which turns out to be far fewer than those supporting sockets.