Something

#!/usr/bin/perl
use strict;

my $baseurl = 'http://hellboundhackers.org/challenges/real2/backups/backup-2004-09-';
my @hours = (
            "0000","0100","0200","0300",
            "0400","0500","0600","0700",
            "0800","0900","1000","1100",
            "1200","1300","1400","1500",
            "1600","1700","1800","1900",
            "2000","2200","2300","2400");

for (my $day = 1; $day <= 31; $day++)  {
   foreach my $hour(@hours) {
      my $url = $baseurl;
      $url .= $day;
      $url .= "_$hour.sql";
      print "$url\n";
   }
}