~= operator in Swift
<p>I recently downloaded the <strong>Advanced NSOperations</strong> sample app from Apple and found this code...</p>

<pre><code>// Operators to use in the switch statement.
private func ~=(lhs: (String, Int, String?), rhs: (String, Int, String?)) -&gt; Bool {
    return lhs.0 ~= rhs.0 &amp;&amp; lhs.1 ~= rhs.1 &amp;&amp; lhs.2 == rhs.2
}

private func ~=(lhs: (String, OperationErrorCode, String), rhs: (String, Int, String?)) -&gt; Bool {
    return lhs.0 ~= rhs.0 &amp;&amp; lhs.1.rawValue ~= rhs.1 &amp;&amp; lhs.2 == rhs.2
}
</code></pre>

<p>It seems to use the <code>~=</code> operator against <code>Strings</code> and <code>Ints</code> but I've never seen it before.</p>

<p>What is it?</p>