Version 4 of exec on windows oddity?

Example-1:

         tk_messageBox -message "before"
         exec -- [auto_execok cmd] << {
                 notepad
                 sleep 5
         } &
         tk_messageBox -message "after"

With example-1, everything works as expected:

1. the start message appears - it has to be confirmed
2. notepad starts (this by itself is an asynchron process)
3. sleep starts
4. the stop message appears immediately (because the whole cmd is started in background with &)
5. after 5 seconds sleep ends
6. notepad is still running

• The main window of the tk prog stays responsive all the time.-

Example-2:

         tk_messageBox -message "before"
         exec -- [auto_execok cmd] << {
                 notepad
                 sleep 5
         }
         tk_messageBox -message "after"

With example-2, things are slightly different:

1. the start message appears - it has to be confirmed
2. notepad starts
3. sleep starts
4. the stop message appears immediately (because the whole cmd is started in background with &)
5. after 5 seconds sleep ends
6. notepad is still running

• The main window of the tk prog stays responsive all the time.-