diff -up perl-5.10.0/lib/CGI.pm.tied perl-5.10.0/lib/CGI.pm
--- perl-5.10.0/lib/CGI.pm.tied	2008-07-30 08:37:48.000000000 +0200
+++ perl-5.10.0/lib/CGI.pm	2008-07-30 08:41:38.000000000 +0200
@@ -1176,7 +1176,7 @@ END_OF_FUNC
 
 'EXISTS' => <<'END_OF_FUNC',
 sub EXISTS {
-    exists $_[0]->{$_[1]};
+    exists $_[0]->{param}{$_[1]};
 }
 END_OF_FUNC