regular expression
<p>need regular expression which could match a string like that <code>"1B7FL26X3WS731388"</code>. Alphanumeric 17 character lenght. </p>

<p>I am using this expression.</p>

<pre><code>$rEX    =  '/([A-Z0-9]){17}/';
</code></pre>

<p>but it also return a portion from a string like this <code>"FGD798791B7FL26X3WS731388POPOD"</code>;</p>

<p>I need to select a string which is exactly 17 character long 18th character should not be Alphanumeric.</p>
