there are several modules :

Crypt::Blowfish Dave Paris

my $cipher = new Crypt::Blowfish $key;
my $ciphertext = $cipher->encrypt($plaintext);
[download]

Crypt::Blowfish_PP Matthew Byng-Maddick

$blowfish=new Crypt::Blowfish_PP($key);
[download]

Now as a general rule your key, should be as random as possible...

UPDATE :
It's not really related to your question but you should give a try to RIJNDAEL the new AES...
Several modules exists, and it's a really good algo.