http://blog.danieroux.com/2008/12/29/dynamic-tasks-with-rake-namespaces

Rakefile.rb

["development", "test", "ci"].each do |databaseName|
  namespace databaseName do
    desc "stop"
    task "stop" do |t|
      puts "Action stop would now be performed on database #{t.scope}"
    end
  end
end