Looks like the data must be padded to be mod 16bytes Here is I think where the error is coming from -- Crypt-Twofish2-0.06/Twofish2.xs:

encrypt(self, data)
     Crypt::Twofish2 self
        SV *    data
        ALIAS:
            decrypt = 1
        CODE:
        {
          SV *res;
          STRLEN size;
          void *rawbytes = SvPV(data,size);

          if (size)
            {
              if (size % (BLOCK_SIZE >> 3))
                croak ("encrypt: datasize not multiple of blocksize (%
+d bits)", BLOCK_SIZE);

              RETVAL = NEWSV (0, size);
              SvPOK_only (RETVAL);
              SvCUR_set (RETVAL, size);

              if ((ix ? blockDecrypt : blockEncrypt)
                    (&self->ci, &self->ki, rawbytes, size << 3, (void 
+*)SvPV_nolen(RETVAL)) < 0)
                croak ("block(De|En)crypt: unknown error, please repor
+t");
            }
          else
            RETVAL = newSVpv ("", 0);
        }
    OUTPUT:
        RETVAL
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