diff -r 0ffb6e4de10a -r f6dec8af3d80 progs/matcher/re1.sc
--- a/progs/matcher/re1.sc	Fri Oct 10 10:18:05 2025 +0100
+++ b/progs/matcher/re1.sc	Fri Oct 10 12:26:29 2025 +0100
@@ -222,6 +222,7 @@
 
 @main
 def test4() = {
+  val r2 = SEQ(SEQ(CHAR('x'), CHAR('y')), CHAR('z'))
   println(pp(r2))
   println(pp(ders("x".toList, r2)))
   println(pp(ders("xy".toList, r2)))