Dont know of anything similar, but you could just:

require 'yaml'

variable = {
    "first"=> "1",
    "second" => nil,
    "third"=> {
        "inner third 1" => nil,
        "inner third 2"=>"yeah"
    },
    "fourth" => nil
}

<pre><%= variable.to_yaml %></pre>

Not nearly as fancy though :)