I'm not 100% certain of what your asking, do you want the warnings to show up or not show up? Given the above code the warning should show up always. If its not then your program is dying sometime before it gets to that line. The reason it shows up twice I believe is due to Apache, first printing the STDERR of the CGI script in question and then printing its own log information that contains the message again.

As for why your program could be dying, HTML::Template usually wants you to have some <tmpl_var> tags within you loop, if you don't you probably shouldn't initialize it with a $ht->param() call at all.

Hope that helps
Chris