Tests: perl module.

test/perl/errors_print/psgi.pl

@@ -0,0 +1,7 @@
+my $app = sub {
+    my ($environ) = @_;
+
+    my $result = $environ->{'psgi.errors'}->print('Error in application');
+
+    return ['200', ['Content-Length' => '1'], [$result]];
+};