/* Extract the object hash and the output filehandle. */
    SV* obj_sv     = ST(0);
    HV* obj_hash   = (HV*)SvRV(obj_sv);
    SV* out_fh_ref = *(hv_fetch(obj_hash, "fh", 2, 0));
    PerlIO* out_fh = (PerlIO*)SvRV(out_fh_ref);

    err = PerlIO_write( out_fh, buf_start, buf_len );