You could have another job come up and kill it, or it could just check the time and stop itself, something like this:

my $hour = (localtime)[2];
exit if ($hour >= 16);
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If you have another job kill it you'll either need to create a PID file, using something like Proc::PID::File or find the PID by parsing ps output ... assuming you're on a UNIX-like system since you mention using cron.