Fix keys on reference, found by Perl 5.20.

regress/NiHTest.pm

diff --git a/regress/NiHTest.pm b/regress/NiHTest.pm
index 295fc64..76b8cd9 100644
--- a/regress/NiHTest.pm
+++ b/regress/NiHTest.pm
@@ -482,7 +482,7 @@
 	@files_got = sort @files_got;
 	my @files_should = ();
 	
-	for my $file (sort keys $self->{files}) {
+        for my $file (sort keys %{$self->{files}}) {
 		push @files_should, $file if ($self->{files}->{$file}->{result} || $self->{files}->{$file}->{ignore});
 	}