Advice for moving forward with modules

[newrisedesigns]

Thanks to tachyon's tutorial, I was able to come up with a few modules. This module is used to block access to some of my CGI programs based on IP address.

If you have the time, please take a look it. I'm updating some code for work, and I'd like all the core functions to be in a module. Before I get deeper into it, I'd like to know any pointers you'd be willing to offer. What's good to have in a module and what's not? How can I make OO modules and when should/shouldn't I use OO? Any insight or information you have is greatly appreciated.

#!/usr/bin/perl -w

package IPBlock;

use strict;
use Exporter;

use vars qw($VERSION @ISA @EXPORT @EXPORT_OK %EXPORT_TAGS);

use constant BLOCKED_LIST => './data/ip_block.dat';

$VERSION     = 1.00;
@ISA         = qw(Exporter);
@EXPORT      = qw(&checkIP);
@EXPORT_OK   = qw(&checkIP &blockIP &unblockIP &returnIP);
%EXPORT_TAGS = (DEFAULT => \@EXPORT,
        ALL    => [qw(&checkIP &blockIP &unblockIP &returnIP)]);

sub checkIP {

    # returns 1 if blocked
    # returns 0 if not blocked


    my $ip = shift;

    open(my $fh, BLOCKED_LIST) or die("Cannot open r BLOCKED_LIST $!")
+;
    flock($fh, 4);

    my $returnvalue = 0;

    while(<$fh>){
        chomp;
        if($_ =~ /\A$ip/){
            $returnvalue = 1;
            last;
        }        
    }

    close($fh);

    return $returnvalue;

}

sub blockIP {

    my $ip = shift;

    open(my $fh, '+<', BLOCKED_LIST) or die("Cannot open r/w BLOCKED_L
+IST $!");
    flock($fh, 2);
    my @block = <$fh>;

    chomp(@block);

    my $returnvalue = 1;

    if( grep(/\A$ip/, @block) ){
        $returnvalue = 0;
    }

    if($returnvalue == 1){
        push(@block, $ip);

        seek($fh, 0, 0);
        truncate($fh, 0);

        print $fh "$_\n" foreach(@block);
    }

    close($fh);

    return $returnvalue;

}

sub unblockIP {

    my $ip = shift;

    open(my $fh, '+<', BLOCKED_LIST) or die("Cannot open r/w BLOCKED_L
+IST $!");
    flock($fh, 2);
    my @block = <$fh>;

    chomp(@block);

    my $returnvalue = 0;

    if( grep(/^$ip/, @block) ){
        @block = grep(!/\A$ip/, @block);
        $returnvalue = 1;
    }

    seek($fh, 0, 0);
    truncate($fh, 0);

    print $fh "$_\n" foreach(@block);
    close($fh);

    return $returnvalue;

}
sub returnIP{

    open(my $fh, '+<', BLOCKED_LIST) or die("Cannot open r/w BLOCKED_L
+IST $!");
    flock($fh, 4);
    my @block = <$fh>;
    close($fh);
    chomp(@block);

    return \@block;

}

1;

Many thanks,
John J Reiser
newrisedesigns.com