Use Return::MultiLevel to wrap route dispatch.

As suggested in #432, use Return::MultiLevel to wrap route dispatch.
Cache the multilevel return coderef in the context for forward/redirect
to use.

Add Return::MultiLevel to prereqs and Scope::Upper to recommends.

dist.ini

@@ -73,7 +73,7 @@ URI::Escape = 0
 parent = 0
 Template::Tiny = 0
 Class::Load = 0
-
+Return::MultiLevel = 0
 
 [Prereqs / Recommends]
 ; Serializers
@@ -94,6 +94,7 @@ Crypt::URandom = 0
 ; extract pod data from apps
 Pod::Simple::Search = 0
 Pod::Simple::SimpleTree = 0
+Scope::Upper = 0
 
 [Prereqs / Suggests]
 ; Used by Dancer2::Session::YAML

lib/Dancer2/Core/Context.pm

@@ -284,4 +284,17 @@ sub destroy_session {
     return;
 }
 
+
+=attr with_return
+
+Used to cache the coderef from L<Return::MultiLevel> within the dispatcher.
+
+=cut
+
+has with_return => (
+    is        => 'rw',
+    predicate => 1,
+    clearer   => 'clear_with_response',
+);
+
 1;

lib/Dancer2/Core/Dispatcher.pm

@@ -8,6 +8,8 @@ use Dancer2::Core::Types;
 use Dancer2::Core::Context;
 use Dancer2::Core::Response;
 
+use Return::MultiLevel qw(with_return);
+
 has apps => (
     is      => 'rw',
     isa     => ArrayRef,
@@ -65,9 +67,20 @@ sub dispatch {
 
             $context->request->_set_route_params($match);
 
-            my $response = $self->_dispatch_route($route, $context);
-
-            return $response if $response->is_halted;
+            my $response = with_return {
+                my ($return) = @_;
+                # stash the multilevel return coderef in the context
+                $context->with_return($return) if ! $context->has_with_return;
+                return $self->_dispatch_route($route, $context);
+            };
+            # Ensure we clear the with_return handler
+            $context->clear_with_response;
+
+            # No further processing of this response if its halted
+            if ( $response->is_halted ) {
+                $app->context(undef);
+                return $response;
+            }
 
             # pass the baton if the response says so...
             if ( $response->has_passed ) {