[Zope] object property which has name defined in variable

Dear all, It is unbelievable, but I does not know how to show title property from object defined in variable like this example: <dtml-let picture="'z4_03_2.jpg'"> <dtml-var "_['picture'].title"> </dtml-let> It returns <built-in method title of string object at 02EB8730> but <dtml-var "_['z4_03_2.jpg'].title"> returns real title from object named z4_03_2.jpg. I am very sorry for this basic question. Many thanks and Best Regards, J. Lukesh