file.rb

use Rack::If, {:path => /\A\/admin\/mega-admin.*/}, :any, :skip do
  use EasyRackOpenID, :allowed_identifiers => ['http://example.com/mega-admin']
end

# If a person goes to /admin/mega-admin and passes that check, they skip this one:
use Rack::If, {:path => /\A\/admin.*/}, :any do
  use EasyRackOpenID, :allowed_identifiers => ['http://example.com/admin']
end

run Site.new