You need to decide whether you want an output terminal, output to a file, where to log to, etc. Usually programs that run constantly are put into a background process or daemonized. You can daemonize most scripts with Proc::Daemon

See How to know if a perl script is put in the background too, for monitoring background processes.

Another consideration, is where you start and stop the program. If you are on linux, there are scripts that run at startup and shutdown, and you can work your script into that mechanism, for automatic start/stop with powerup/powerdown events.

You really should be more specific in what type of script you envision running.