In perl6.....

#!/usr/bin/pugs
use v6;

rule minute {  <[1..5]>?\d   | <[*]> };
rule hour   {  <[1..2]>?\d   | <[*]>  };
rule day    {  31 | 30       | <[1..2]>?\d   |   <[*]>   }
rule month  {  1?\d          | <[*]>  }
rule day_of_week { <[0..6]>  | <[*]> }

rule crontab { <minute> \s+ <hour> \s+ <day> \s+ <month> \s+ <day_of_w
+eek> }


my $crontab = "0 10 * * *" ~~ /<crontab>/;
my $match = $crontab<crontab>;
say "Minute: $match<minute>\nHour:   $match<hour>\n"
  ~ "Day:    $match<day>\nMonth:  $match<month>\n"
  ~ "Day of Week: $match<day_of_week>";
[download]

1;0 eric256@feather:~/tests$ pugs crontab.p6
Minute: 0
Hour:   10
Day:    *
Month:  *
Day of Week: *
[download]