Its a bug in wxWidgets. If you add

Wx::Event::EVT_CHAR(  $entry, sub{warn"@_"; $_[1]->Skip; });
[download]

you can see that the problem is upstream (Skip signals to call the upstream event handler, which is the default handler, but there is a disconnect and it doesn't get called)

You could work around the problem by handling the event yourself, but thats just busy work.

The real solution is to submit a bug report for both wxperl/wxwidgets.