 <p>How is this using <a href="http://apidock.com/ruby/Object/initialize_copy" rel="nofollow"><strong><em><code>initialize_copy</code></em></strong></a>:</p> <pre><code>a=[] b=[] a.object_id # =&gt; 11512248 b.object_id # =&gt; 11512068 b.send(:initialize_copy,a &lt;&lt; 10) a # =&gt; [10] b # =&gt; [10] a.object_id # =&gt; 11512248 b.object_id # =&gt; 11512068 </code></pre>