my %dispatch = (
   home   => \&default,
   donate => \&default,
   news   => \&default,
   samp   => sub { \&samples($dbh) },
   ...
);

$action = $apr->param('a');
$action = 'home' if !exists $dispatch{$action};
$dispatch{$action}->($action);

sub default {
   my ($action, $params) = @_;
   return render_template($action, $params);
}

sub samples {
   my ($action, $dbh) = shift;
   ...
}

##</code><code>##

my %dispatch = (
   (map { $_ => \&default } qw(
      home donate news
   )),
   samp => sub { \&samples($dbh) },
   ...
);