Calls the System V IPC function shmctl. 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 shmid_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 IPC::SysV documentation.