setpgrp

setpgrp pid, pgrp

Sets the current process group pgrp for the specified pid (use a pid of 0 for the current process). Invoking setpgrp will produce a fatal error if used on a machine that doesn't implement setpgrp(2). Some systems will ignore the arguments you provide and always do setpgrp(0, $$). Fortunately, those are the arguments you usually provide. (For better portability, use the setpgid() function in the POSIX module, or if you're really just trying to daemonize your script, consider the POSIX::setsid() function as well.)