Below are examples of cron jobs. I hope this information will help you better understand how this program works.
# perform the task once per hour for 0 minutes
0 */1 * * * /home/u12345/script.pl
# perform the task every three hours at 0 minutes
0 */3 * * * /home/u12345/script.pl
# complete the task on mondays at 1:15 a.m.
15 1 * * 1 /home/u12345/script.pl
# complete the task on april 5 at 0 o'clock 1 minute every year
1 0 5 4 * /home/u12345/script.pl
# complete the task on Friday the 13th at 13:13
13 13 13 * 5 /home/u12345/script.pl
# complete the task every month on the 1st at 6:10 am
10 6 1 * * /home/u12345/script.pl