Specs for where $_ is defined and when it is defined?

To avoid clashes between specs, we need to isolate things like defining classes and methods. The style guide states that all constants should be scoped to a module (eg LanguageSpecs). In this case, it would be fine to use an anonymous class and instance, eg:

```ruby
klass = Class.new do
  def dollar_under
    # ...
  end
end
```