I only have a workaround: set a break (or continue to the point) where %hash is initialized. Then create a reference to that hash with $href = \%hash, and watch with w $href->{'myEntry'}.

The variables you define in the debugger don't go out of scope. But note that the behavior of your code will change if you want %hash to go out of scope and maybe be re-initialized later: As long as the reference lives, %hash will stick around.