Ah, it seems that the issue when typing a bracket is related to the debugger. I'm working with Komodo IDE.
I do not get a Perl error message, it just crashes and then shows a generic Windows error notification (Perl Command Line Interpreter stopped working).
Without the debugger, I do get the same result when pressing tab and then shift + tab.
I can't reproduce it at the moment, but I once also saw a debugger warning about deep recursion for focusPrev.
The method looks as follows:
my $w = shift;