If you're using CGI.pm, which is a good idea to use when writing perl/cgi scripts, you can take advantage of it's built in cookie support.

The relevant section in the documentation states that "Negative expiration times (e.g. "-1d") cause some browsers to delete the cookie from its persistent store. This is a poorly documented feature.".

Here's some sample code to help you delete a cookie:

    my $cookie = $query->cookie (           
        -name => 'foo',           
        -value => 'bar',           
        -expires => '-1d',           
        -path => '/',           
        -domain => 'my.domain.com'          
    );

    print $query->header(-cookie=>$cookie);
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