I can confirm that behaviour. Particularly weird is that if you print out $ENV{QUERY_STRING}, you can actually see the current proper values being passed in via the URL (GET request) — the param() method, however, continues to return the first-time value unchanged. It apparently doesn't reparse the available new input.  It doesn't even help to explicitly call $q->delete("name") or $q->delete_all() at the end of the request cycle...

Well, for the moment, I don't have a solution other than to suggest that you use CGI::Simple instead, which doesn't suffer from this problem (it's a CGI drop-in replacement for most things you typically need, i.e. you'd just do my $q = new CGI::Simple; and then call $q->param(...) etc. as usual).