Mysql::Statement     O_HvRV
Mysql            O_HvRV

INPUT
T_HVOBJ
     if (sv_isobject($arg))
         $var = (HV*)SvRV($arg);
     else
         croak(\"$var is not an object\")
O_HvRV
        if( sv_isobject($arg) && (SvTYPE(SvRV($arg)) == SVt_PVHV) )
                $var = (HV*)SvRV( $arg );
        else {
                warn( \"${Package}::$func_name() -- $var is not a blessed HV reference\" );
                XSRETURN_UNDEF;
        }
OUTPUT
T_HVOBJ
     $arg = newRV((SV*)$var);

