perldoc > setpgrp

    setpgrp PID,PGRP
            Sets the current process group for the specified PID, 0 for the
            current process. Raises an exception when used on a machine that
            doesn't implement POSIX setpgid(2) or BSD setpgrp(2). If the
            arguments are omitted, it defaults to "0,0". Note that the BSD
            4.2 version of "setpgrp" does not accept any arguments, so only
            "setpgrp(0,0)" is portable. See also POSIX::setsid().

            Portability issues: "setpgrp" in perlport.