=over =item 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 C, then ARG must be a variable which will hold the returned C structure. Returns like ioctl: the undefined value for error, "C<0> but true" for zero, or the actual return value otherwise. See also L and C documentation. =back