And some of the viable options if multi-c++-version support is a necessity (as proposed by Klugier and me):

1. [=] to [&] when necessary. Make local copies of variables that are originally captured by value with undesired modification, and refer only to the copy in the lambda body. A fictitious example:

struct MyApp : TopWindow {
   Button b;

   MyApp() {
       int j = 12;
       b << [&] { PromptOK(AsString(j)); };
   }
};