samplecap.rb

# call with cap -S only_host=monkeypants
only_host ||= nil

role(:monkey) do 
  if only_host
    [ only_host ]
  else
    [ :static, :host, :list ]
  end
end

role(:database) do
  ...
end

task :foo, :roles => [ :monkey ] do
  bar
end

task :bar, :roles => [ :database ] do
 # 
end