Crypt::Blowfish encrypts just a block (your 8 bytes) at a time; you'll need another module to handle real data. Splitting your data in 8-byte blocks, encrypting each, and combining is the obvious but insecure way to do this; Cipher Block Chaining is a method for doing it securely. As Aristotle mentions, Crypt::CBC will do the work for you with a wee bit of effort; Crypt::CBCeasy is supposed to make things Just Work in a way like what you want. You should be able to do this
in reply to Encrypting strings with more than 8 bytes.
my $key = pack("H16", "0123456789ABCDEF"); # min. 8 bytes
my $ciphertext = Blowfish::encipher($key, "my string has lots of bytes
print unpack("H16", $ciphertext), "\n";
my $deciphertext = Blowfish::decipher($key, $ciphertext);
print $deciphertext, "\n";