THRIFT-4717: fix up make clean with autoconf
diff --git a/test/perl/Makefile.am b/test/perl/Makefile.am
index 165b9a7..1dbaf28 100644
--- a/test/perl/Makefile.am
+++ b/test/perl/Makefile.am
@@ -25,5 +25,7 @@
 check: stubs
 
 clean-local:
-	$(RM) -r gen-perl
+	$(RM) -r gen-perl/
 
+dist-hook:
+	$(RM) -r $(distdir)/gen-perl/