Tests: Perl streaming body and delayed response simple tests.

test/perl/delayed_response/psgi.pl

@@ -0,0 +1,10 @@
+my $app = sub {
+    my ($environ) = @_;
+
+    return sub {
+        (my $responder = shift)->([200, [
+            'Content-Type' => 'text/plain',
+            'Content-Length' => '12'
+        ], ["Hello World!"]]);
+    }
+};