Use iterators instead of file lists

Change-Id: I49ea1075939d8e0d042d15556ea16db9359d3aff
diff --git a/.gitignore b/.gitignore
index 28b98b2..f57405c 100644
--- a/.gitignore
+++ b/.gitignore
@@ -40,3 +40,5 @@
 t/real/corpus/AGD-orig
 t/real/corpus/FOLK-orig
 t/real/dck.t
+t/real/corpus/TWI21
+t/real/corpus/WPD15
\ No newline at end of file