t/perf/optree.t: expand blurb

explain (kind of) why this file is called optree.t

diff --git a/t/perf/optree.t b/t/perf/optree.t
index ef8649f..dac0a25 100644 (file)
--- a/t/perf/optree.t
+++ b/t/perf/optree.t
@@ -1,6 +1,7 @@
 #!./perl
 
-# Use B to test that optimisations are not inadvertently removed.
+# Use B to test that optimisations are not inadvertently removed,
+# by examining particular nodes in the optree.
 
 BEGIN {
     chdir 't';