sub handler {
   # use Apache2::Request; is in startup.pl
   my $r = Apache2::Request->new(shift);
   my $shipaddr2 = $r->param("shipaddr2");
...
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I think it's not so much the $r object and its params, but rather some other data structure that's retaining the values.  At least, in your original post, it isn't clear where %ship_address comes from, how data gets into it, if it's global (which could be the problem), or if you do empty it on every request, etc.  In other words, it's hard to provide anything else than general hints without seeing the actual (complete) code...

Thanks for your patience. I'll abstract: Perl handler to capture form submission data:

sub handler {
   my $r = Apache2::Request->new(shift);
   my %in_cookies = Apache2::Cookie->fetch ($r);
   my $session = $in_cookies{"ID"} && $in_cookies{"ID"}->value;
   
   my $dbh = DBI->connect('DBI:mysql:mydb', 'myuser', 'mypasswd', { Ra
+iseError => 1, AutoCommit => 1, PrintError => 1} ) or die $DBI::errst
+r;
   my $shipaddr1 = $r->param("shipaddr1");
   my $shipaddr2 = $r->param("shipaddr2");
   my %ship_address = (addr1 => $shipaddr1, addr2 => $shipaddr2);
   unless ($dbh->selectrow_array("select count(*) from bill where sess
+ion=?",undef,$session)){ # new entry
      $dbh->do("insert into bill (session) values(?)",undef,$session);
      while ( my ($key,$value) = each %ship_address ) {
         $dbh->do("update bill set ship$key = ? where session = ?", un
+def, $value, $session);
      }
   }
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Difficulty: if the form does not contain data for shipaddr2 then shipaddr2 can contain data from a previous call to the handler.