(Note: I have that sneaking suspicion it was you, harryC, who downvoted me (for trying to help), so you'll understand that my follow-up response is somewhat less verbose than it would be otherwise...   UPDATE: it turned out my suspicion was wrong. I'm sorry for that!)

So, yes, I do think you more or less have the scenario I decribed: you do not specify an "action" URI when you call start_form, so CGI.pm will submit to itself (the default), i.e. the URI that generated the page/form...   and thus put the parameters received as initial values into the subsequent form on the response page (this is default magic of CGI.pm).

What you want is: extract the parameters you need (like $verwerken = param('Doorsturen'), etc.), then call $q->delete_all. Both needs to be done before you output the form with $q->start_form .

Alternatively, in particular if you don't really want the form at all on the response page, specify -action => $some_other_URI as argument to start_form(), and generate the response page via some other CGI script...