diff --git a/tools/test_modules/m21400.pm b/tools/test_modules/m21400.pm
index 7446133b3..daaa02108 100644
--- a/tools/test_modules/m21400.pm
+++ b/tools/test_modules/m21400.pm
@@ -1,3 +1,5 @@
+#!/usr/bin/env perl
+
 ##
 ## Author......: See docs/credits.txt
 ## License.....: MIT