title: Equivalent to Ruby's #tap method in Scala
body: <p>Ruby has a method that allows us to observe a pipeline of values, without modifying the underlying value:</p>
  
  <pre><code># Ruby
  list.tap{|o| p o}.map{|o| 2*o}.tap{|o| p o}
  </code></pre>
  
  <p>Is there such a method in Scala? I believe this is called a Kestrel Combinator, but can't be sure.</p>