Don't know what your problem actually is. But I remember your error was "data not in block size 16". What the sub does is pad the string with null characters, from 1 to 15 depending, so that the data string is in nice even blocks of 16 bytes. You will see that after you decrypt, the data will be a little bigger because of the padding, but it won't affect the file. If you want to strip the file after decrypting:

#To strip any padding after decryption: 
my $plaintext = $cipher->decrypt($encrypted); 
   $plaintext =~ s/^\0+//;
[download]

Why you are not getting the results you want is not known to me. Maybe try posting again with some code?