sub safe_from_evil_filehandles(&) {
    my ($cb) = @_;
    my @evil_globs;
    ... # walk through %:: and list all globs
        # where *{$entry}{IO} is defined
        # unless they're OK like "STDOUT"
    my $localizer; $localizer = sub {
        return $cb->() unless @evil_globs;
        local *{shift @evil_globs};
        return $localizer->();
    };
    return $localizer->();
}