So I understood that there is no chance to reuse my previously created window. dumb question: is it not possible to save "Tk::MainWindow=HASH(0xa1eeed8)" like this to a file and re-create the window handler in next run?
Use Tk::WidgetDump, it uses ->configure/->cget/->children and a few other methods to introspect widgets (get their settings properties sizes bindings configuration colors text values data ...)
Thats how you "save" a window to disk, you dump all its ocnfiguration and data ... and later you "load" it from disk ... you use ->configure/->cget/->children.....