Scheduling perl scripts to run at a certain time, or at a certain interval is usually done by some service of the operating system. In Unix/Linux/Mac OSX this can be crontab, and we call the processes cron-jobs.

On Windows there is a service called scheduler that will do the work.

Linux/Unix/Mac OSX

The crontab on Linux/Unix/Mac OSX can be configured by editing a text file with a special command.

Each line in the file is a scheduled job. Empty lines and lines starting with # are disregarded:

The other lines contain 6 values. The first five represent the schedule in the following order: minute, hour, day of month, month, day of week.

The 6th is the actual command.

* at any of the first five slots mean "every" so a * at the first slot means "every minute".

The following crontab will run every minute: 

# m h  dom mon dow   command
* * * * * /home/gabor/perl5/perlbrew/perls/perl-5.18.2/bin/perl /home/gabor/bin/ts.pl >> /home/gabor/ts.out

How to run a Perl script automatically every 12pm

The following crontab will run every day at 12 hour 0 minutes. 

# m h  dom mon dow   command
0 12 * * * /home/gabor/perl5/perlbrew/perls/perl-5.18.2/bin/perl /home/gabor/bin/ts.pl >> /home/gabor/ts.out

Every user in a Unix/Linux system has her own crontab. crontab -l will list the crontab file of the current user. You can prepare a text file (e.g. crontab.txt) describing your cron-jobs with any editor and then load them using crontab path/to/crontab.txt. I usually keep that text file under version-control.

Every hour +0, +20, and +40 minutes: 

0,20,40 * * * * command

Every 2 minutes: 

*/2 * * * * command

MS Windows

MS Windows has a service called Windows Task Scheduler. Use that.