I'm not sure that's really sufficiently clear; a newbie might assume "any perl question about my site" goes there.

As an alternative, maybe use two SUBMIT buttons (or radioboxes) for lower-level monks, one which claims it's a perl-related question, the other that it's about the website, so they have the explicit choice; if they choose the perl-related option, give an error message instead of the normal submission-results:

sub generate_pmd_form {
   ...
   if(level($monk) < $n) { 
      $pmd_form->add_submit("This post is about Perl");
      $pmd_form->add_submit("This post is about the perlmonks website"
+);
   }
   ...
}
...
sub process_pmd_submit {
   if($form_submit eq "This post is about Perl") {
      print err_message("wrong forum; you meant SOPW") 
      return generate_pmd_form();
   }
   ... normal submission acceptance ...
}
[download]

... or maybe a Monk's first N posts to PMD should have the dual-option. Or maybe add an option to display settings that says "☐ I know what PMD is for, and will not post perl-related questions there (turns off the extra SUBMIT/RADIOBOXES for PMD submission)" (default unchecked for new users)

(edit: clarify the display setting defaults to unchecked)