Well, I'm assuming that your not simply checking for the existence of a cookie with your CGI, but rather, you are looking for some specific verifier tht the cookie holds. Why not just recode your script to return an error page if the cookie holds an invalid verifier?
To clarify: Use a session-based system. When a user logs in, write them a cookie with the session ID. At that same time, write the session ID to a local file. When the user is logged out, erase the session ID from the file and if they try to return, their cookie will be checked. When the file is checked for the session ID that their cookie holds, the script won't find anything and can then tell the user to login again or buzzoff.
Are you posting in the right place? Check out Where do I post X? to know for sure.
Posts may use any of the Perl Monks Approved HTML tags. Currently these include the following:
<code> <a> <b> <big>
<blockquote> <br /> <dd>
<dl> <dt> <em> <font>
<h1> <h2> <h3> <h4>
<h5> <h6> <hr /> <i>
<li> <nbsp> <ol> <p>
<small> <strike> <strong>
<sub> <sup> <table>
<td> <th> <tr> <tt>
Snippets of code should be wrapped in
<code> tags not
<pre> tags. In fact, <pre>
tags should generally be avoided. If they must
be used, extreme care should be
taken to ensure that their contents do not
have long lines (<70 chars), in order to prevent
horizontal scrolling (and possible janitor
Want more info? How to link or
or How to display code and escape characters
are good places to start.