Calls the System V IPC function msgctl(2). You'll probably have to say
use IPC::SysV;first to get the correct constant definitions. If CMD is IPC_STAT, then ARG must be a variable that will hold the returned msqid_ds structure. Returns like ioctl: the undefined value for error, "0 but true" for zero, or the actual return value otherwise. See also "SysV IPC" in perlipc and the documentation for IPC::SysV and IPC::Semaphore.
Portability issues: "msgctl" in perlport.