var engine = new Engine();
var obj = new JsObject(engine);
var getterFunction = (IFunction)new Parser().ParseExpression(
     "function() { return 'test'.match(/[a-z]/)?.[0]; }" // Fails
       // "function() { return 'test'.match(new RegExp('[a-z]'))?.[0]; }" // RegExp will work
    );
var getter = new ScriptFunction(engine, getterFunction, true);

obj.FastSetProperty("name", new GetSetPropertyDescriptor(getter, null, true, false));
engine.SetValue("customObj", obj);

engine.Execute(string.Empty);
var result = engine.GetValue("customObj").AsObject();
var name = result.Get("name").ToString();

Console.WriteLine("Property [name]: {0}", name);