require 'main'

Main {
  argument 'x' do
    arity 2

    error :before do |e|
      p e
      puts 'this fires *before* normal error handling using #instance_eval...'
    end

    error do |e|
      p e
      puts 'this fires *instead of* normal error handling using #instance_eval...'
    end
  end
  
  run(){ p param['x'].given? }
}