When using Tk, I observed that my custom debugging signal handler for $SIG{__WARN__} is overwritten by Tk :(.
So I needed to reoverwrite it after use Tk; with my own one again.

use Tk;
...

# if running with debugger, reinstall signal handler
if (defined $DB::single) {
        # avoid warning: '$DB::single' is only used once
        $DB::single = $DB::single;
        DB::afterinit();
}
[download]

Unfortunately this requires modification of the script.

Any suggestions for enhancements are welcome.