Tests: more perl tests.

test/perl/header_equal_names/psgi.pl

@@ -0,0 +1,9 @@
+my $app = sub {
+    my ($environ) = @_;
+
+    return ['200', [
+        'Content-Length' => 0,
+        'Set-Cookie' => 'tc=one,two,three',
+        'Set-Cookie' => 'tc=four,five,six'
+    ], []];
+};