title: Are strings mutable in Ruby?
body: <p>Are Strings mutable in Ruby? According to the <a href="http://www.ruby-doc.org/core/classes/String.html#M001125" rel="noreferrer">documentation</a> doing </p>
  
  <pre><code>str = "hello"
  str = str + " world"
  </code></pre>
  
  <p>creates a new string object with the value <code>"hello world"</code> but when we do </p>
  
  <pre><code>str = "hello"
  str &lt;&lt; " world"
  </code></pre>
  
  <p>It does not mention that it creates a new object, so does it mutate the <code>str</code> object, which will now have the value <code>"hello world"</code>?</p>