#!/usr/bin/perl

use strict;
use warnings;

use DateTime::Event::Cron;

my @crontab = ( '*/3 15 1-10 3,4,5 */2',
                '* * * * 1-4,5-7,11,20',
                '* * * 1-4,5-7,11,20 *',
                '* * 1-4,5-7,11,20 * *',
                '* 1-4,5-7,11,20 * * *',
                '1-4,5-7,11,20 * * * *',
              );

my $set;

foreach my $line (@crontab) {
    eval {
       $set = DateTime::Event::Cron->from_cron( $line );
    };
    print "$line: ", ($@ ? $@ : 'OK'), "\n";
}