logstash.conf

input {
    stdin {}
}

filter {
    grok {
        # Ex: I AM SOME DATA
        match => ["message", "^%{DATA}$"]
    }
    if [data][info][score][value] {
    }
}
output {
    stdout { codec => rubydebug }
}

output.rb

{
       "message" => "I AM SOME DATA",
      "@version" => "1",
    "@timestamp" => "2014-12-27T00:55:11.075Z",
          "host" => "Sauron",
          "data" => {
        "info" => {
            "score" => {}
        }
    }
}