use Crypt::CBC;

$cipher = Crypt::CBC->new(
   -cipher => 'Rijndael',
   ...
);

$cipher->iv($iv);

$ciphertext = $cipher->encrypt("This data is hush hush");
$plaintext  = $cipher->decrypt($ciphertext);

##</code><code>##

use Crypt::CBC;

$cipher = Crypt::CBC->new(
   -cipher => 'Rijndael',
   -iv     => $iv,
   ...
);

$ciphertext = $cipher->encrypt("This data is hush hush");
$plaintext  = $cipher->decrypt($ciphertext);