require 'haml'
engine = Haml::Engine.new(%{
%body
  #welcome-box
    %p= greeting
  %p
    As of
    = Time.now
    the reasons you gave were:
    %table
      %tr
        %th Reason
        %th Rank
      - for reason in reasons
        %tr
          %td= reason[:reason_name]
          %td= reason[:rank]
})

data = {
  greeting: 'Hello, Dave Thomas',
  reasons: [
    { reason_name: 'flexible',    rank: '87' },
    { reason_name: 'transparent', rank: '76' },
    { reason_name: 'fun',         rank: '94' },
  ]
}

puts engine.render(nil, data)

/Users/andrekibbe/.rvm/gems/ruby-2.2.1/gems/haml-4.0.7/lib/haml/engine.rb:136:in `block in render': can't modify frozen NilClass (RuntimeError)
    from /Users/andrekibbe/.rvm/gems/ruby-2.2.1/gems/haml-4.0.7/lib/haml/engine.rb:135:in `instance_eval'
    from /Users/andrekibbe/.rvm/gems/ruby-2.2.1/gems/haml-4.0.7/lib/haml/engine.rb:135:in `ensure in render'
    from /Users/andrekibbe/.rvm/gems/ruby-2.2.1/gems/haml-4.0.7/lib/haml/engine.rb:135:in `render'
    from haml_example.rb:17:in `<main>'