perldoc > getpriority

    getpriority WHICH,WHO
            Returns the current priority for a process, a process group, or
            a user. (See getpriority(2).) Will raise a fatal exception if
            used on a machine that doesn't implement getpriority(2).

            "WHICH" can be any of "PRIO_PROCESS", "PRIO_PGRP" or "PRIO_USER"
            imported from "RESOURCE CONSTANTS" in POSIX.

            Portability issues: "getpriority" in perlport.