title: YAML - substituting values for variables?
body: <p>consider the following yaml  </p>
  
  <pre><code>hadoop:  
     storage: '/x/y/z/a/b'
     streaming_jar_path: '/x/c/d/f/r/*.jar'
     commands:  
         mkdir: 'hadoop dfs -mkdir dir'
         copyFromLocal: 'hadoop dfs -copyFromLocal from_path to_path'  
         run: 'hadoop jar $streaming_jar_path -mapper mapper_path -reducer reducer_path -input hdfs_input -output hdfs_output'  
  </code></pre>
  
  <p>I want to substitute the value of <code>streaming_jar_path</code> to <code>$streaming_jar_path</code>, how can I do that?  </p>
  
  <p>I know we can <code>merge</code> the <code>hashes</code> using <code>&amp;(anchors)</code> but here i just want to change one value<br>
  I am sorry if this is trivial thing, I am very new to <code>YAML</code>  </p>
  
  <p>Thank you</p>