Hi,
The CGI module returns the list on request, using wantarray to determine your wishes. See the CGI docs.
just modify your code a bit:

foreach($q->param()){
  if(/^\w\d+/){
    $stuff .= $_; $stuff .= ":";
    my @v;
    $stuff .= join ',', (@v = $q->param("$_"));
    $stuff .= "\n\n";
  }
}

-anders