platform agnostic

I was recently looking for a Perl Captcha implementation that’d generate number-only Captchas. I looked inside Authen::Captcha and figured I could subclass it do just numeric captchas. It turned out to be a lot simpler than I thought it would be. Here is the code:

package Authen::NumCaptcha;

use strict;
use base qw(Authen::Captcha);

sub new {
    my $class = shift;
    my $captcha = $class->SUPER::new( @_ );
    return bless $captcha, $class;
}

sub generate_random_string {
    my $self = shift;
    my $length = shift;

    my $code = "";
    my $char;

    for (my $i=0; $i < $length; $i++) {
        $char = int(rand 7)+50;
        $char = chr($char);
        $code .= $char;
    }

    return $code;
}

1;

We basically override Authen::Captcha's generate_random_string and only use ASCII characters 50 to 57 (digits 2 to 9). Authen::Captcha doesn't include the digits 0 and 1 because they could be confused with oh (O) and lower case elle (l) or upper case ai (I).

To use Authen::NumCaptcha, place it under /usr/share/perl5/Authen/ (or wherever you have Authen::Captcha installed) alongside Captcha.pm. Then use it as you'd use Auhten::Captcha. For example:

use Authen::NumCaptcha;

my $num_chars = 6;
my $num_captcha = Authen::NumCaptcha->new (
                                          data_folder => '/tmp',
                                          output_folder => '/tmp'
                                          );

my $num_md5sum = $num_captcha->generate_code($num_chars);