Crypt/Blowfish.pm:
        Crypt::Blowfish::crypt($data, $data, $self->{'ks'}, 0);

Crypt/Blowfish.xs:
void
blowfish_crypt(input, output, ks, dir)
        char *  input = NO_INIT
        SV *    output
        char *  ks = NO_INIT
        STRLEN  input_len = NO_INIT
        STRLEN  output_len = NO_INIT
        STRLEN  ks_len = NO_INIT
        int             dir
        CODE:
        {
                input = (char *) SvPV(ST(0), input_len);
                if (input_len != 8)
                        croak("input must be 8 bytes long");