I'd prefer not to add new string evals (see #862), and this is a bit of an obtuse way to get `main`.  What do you think about doing this instead?

``` ruby
module RSpec
  module Core
    class Runner
      class << self
        attr_accessor :main
      end
    end
  end
end

RSpec::Core::Runner.main = self
```

...then you can just get `main` from the `main` attribute.