use warnings;

package Grief;
use overload
    '='    => \&_copy;


use Inline C => Config =>
    BUILD_NOISY => 1;

use Inline C => <<'EOC';

typedef struct {
    long num;
} Number;

SV * new(SV * x) {
     Number * num_obj;
     SV * obj_ref, * obj;

     New(1, num_obj, 1, Number);
     if(num_obj == NULL)
      croak("Failed to allocate memory in new() function");
     obj_ref = newSViv(0);
     obj = newSVrv(obj_ref, "Grief");
     num_obj->num = SvUV(x);

     sv_setiv(obj, (IV)num_obj);
     SvREADONLY_on(obj);
     return obj_ref;
}

SV * _get_val(SV * obj) {
     return newSVuv(((Number*)SvIV(SvRV(obj)))->num);
}

void _set_val(SV * obj, SV * x) {
     ((Number*)SvIV(SvRV(obj)))->num = SvUV(x);
}

SV * _copy(SV * arg_obj, SV * second, SV * third) {
     Number * num_obj;
     SV * obj_ref, * obj;

     New(1, num_obj, 1, Number);
     if(num_obj == NULL)
      croak("Failed to allocate memory in _copy() function");
     obj_ref = newSViv(0);
     obj = newSVrv(obj_ref, "Grief");
     num_obj->num = ((Number*)SvIV(SvRV(arg_obj)))->num;

     sv_setiv(obj, (IV)num_obj);
     SvREADONLY_on(obj);
     return obj_ref;
}

SV * _set_from_existing(SV * arg_obj) {
     Number * num_obj;
     SV * obj_ref, * obj;

     New(1, num_obj, 1, Number);
     if(num_obj == NULL)
      croak("Failed to allocate memory in _set_from_existing() function");
     obj_ref = newSViv(0);
     obj = newSVrv(obj_ref, "Grief");
     num_obj->num = ((Number*)SvIV(SvRV(arg_obj)))->num;

     sv_setiv(obj, (IV)num_obj);
     SvREADONLY_on(obj);
     return obj_ref;
}

void DESTROY(SV * obj) {
    printf("Destroying ...");
    Number * number = (Number*)SvIV(SvRV(obj));
    Safefree(number);
    printf("... destroyed\n");
}


EOC

$num1 = Grief::new(113);
$num2 = $num1; # Assign using _copy()
$num3 = _set_from_existing($num1); # Assign using _set_from_existing()
_set_val($num1, 555);
print _get_val($num2),"\n", _get_val($num3), "\n";
__END__
Outputs:
555
113
Destroying ...... destroyed
Destroying ...... destroyed