new_default.rb

ruby_block "randomly_choose_language" do
  block do
    if Random.rand > 0.5
      node.run_state['scripting_language'] = 'php'
    else
      node.run_state['scripting_language'] = 'perl'
    end
  end
end

package "scripting_language" do
  package_name lazy { node.run_state['scripting_language'] }
  action :install
end