my favorite way to block people has lot's of watcher daemons sending block requests to a database, and a blocker daemon that updates firewall-filters at the border. no muss, no fuss. (it's a current project, can't 'ya tell? =)

Net::Netmask has everything you need for blocking whole ranges of ip's, but it might not be easy to serialize to/from a file.

if i were you, i would have done something with one of the Cache::Cache modules:

# untested, but close.
$blocked = Cache::FileCache->new(
  cache_root => '/wherever/blocked_hosts',
  default_expires_in => '30 days',
) or die "no cache!\n";

sub block {   # block($ip,$howlong)
  $blocked->set($_[0], 1, $_[1]);  
}

sub is_blocked {  # is_blocked($ip) -> undef or 1
  $blocked->get($_[0]);
}

sub unblock {  # unblock($ip)
  block($_[0], 'now');  # expire 'now', $ip go poof!
}


block('192.168.254.1');   # 30 days
block('192.168.254.12','6 months');
deny_access if is_blocked('192.168.254.1');
unblock('192.168.254.1');
block('192.168.254.13', 'never');  # block forever!
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the auto expire can come in quite handy.

or if you can, a decent database, DBI and some SQL will let you easily access the blocked info from anywhere w/o worrying about locking and such, plus you can store the IP and Mask in the database as Integer values and then build a SELECT that will match ranges using SQL's math operators.

$is_blocked = $dbh->prepare('
SELECT 1 FROM blocks WHERE
( ? & mask ) == ( ip & mask )
');

deny_access if ($is_blocked->execute(ip2int('192.168.254.1')));

# blocks
#  ip integer,
#  mask integer
1.0.0.0  == 16777216
1.1.0.0  == 16842752
1.1.1.1  == 16843009
255.255.0.0 == 4294901760

16777216 & 4294901760 == 16777216
16842752 & 4294901760 == 16842752
16843009 & 4294901760 == 16842752

so... blocks
ip          mask
16842752    4294901760   (1.1.0.0 255.255.0.0)

will block everything under 1.1.0.0/16
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or since TMTOWTDI i'm pretty sure CPAN has something that will tie a hash to a file/db

tie %blocks, 'Tie::Foo', 'the_block_file';
sub block { $blocks{shift} = 1 }
sub unblock { delete $blocks{shift} }
sub is_blocked { exists $blocks{shift} }
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