```ruby
require "the_merger/version"

module TheMerger
  def self.merger
    puts 'Mail Merge test'
  end
  
  def self.merge_fields(original_body, *fields)

    User.all.each do |user|
      puts "User: #{user.firstname}"
      
      body = original_body.dup
      
      fields.each do |field|
        body = body.gsub!("[#{field}]", user.send(field))
        puts "body = #{body}"
      end
    end
  end

  
end
```

Read a variable from a yaml file
user
```ruby
require "the_merger/version"

module TheMerger
  #
  # Default settings for TheMerger
  # 
  # merge_model:   User
  #
  
  def self.merger
    puts 'Mail Merge test'
  end
  
  def self.merge_fields(original_body, *fields)
    self.parse_config
    puts @merge_model
    
    User.all.each do |user|
      puts "User: #{user.firstname}"
      
      body = original_body.dup
      
      fields.each do |field|
        body = body.gsub!("[#{field}]", user.send(field))
        puts "body = #{body}"
      end
    end
  end

  private

  def self.parse_config
    path = "#{Rails.root}/config/the_merger.yml"
    
    if File.exists?(path)
      conf=YAML::load(IO.read(path))
      @merge_model = conf["merge_model"]
    else
      @merge_model = "User"
    end
  end  
end
```
assistant