setpriority

See the current Perl documentation for setpriority.

Here is our local, out-dated (pre-5.6) version:

setpriority - set a process's nice value

setpriority WHICH,WHO,PRIORITY

Sets the current priority for a process, a process group, or a user. (See setpriority(2).) Will produce a fatal error if used on a machine that doesn't implement setpriority(2).