Perl5 リファレンス

       semctl ID,SEMNUM,CMD,ARG
               Calls the System V IPC function `semctl'.  You'll
               probably have to say

                   use IPC::SysV;

               first to get the correct constant definitions.  If
               CMD is IPC_STAT or GETALL, then ARG must be a
               variable which will hold the returned semid_ds
               structure or semaphore value array.  Returns like
               `ioctl': the undefined value for error, "`0 but
               true'" for zero, or the actual return value
               otherwise.  The ARG must consist of a vector of
               native short integers, which may may be created
               with `pack("s!",(0)x$nsem)'.  See also `IPC::SysV'
               and `IPC::Semaphore' documentation.