shmctl ID,CMD,ARG
            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: "undef" for
            error; "0 but true" for zero; and the actual return value
            otherwise. See also "SysV IPC" in perlipc and "IPC::SysV"
            documentation.

            Portability issues: "shmctl" in perlport.