--- a/progs/catastrophic.rb	Tue Sep 25 21:57:14 2018 +0100
+++ b/progs/catastrophic.rb	Fri Sep 28 13:54:18 2018 +0100
@@ -1,14 +1,14 @@
 # A case of catastrophic backtracking in Ruby
 #---------------------------------------------
+# example provided by Daniel Baldwin
 #
+# 
 # regex: (a?){n} a{n}
 # strings: aa...
 #
-# example provided by Daniel Baldwin
+# run on the command line with:
 #
-# call with:
-#
-#   > ruby catastrophic.rb
+# $>  ruby catastrophic.rb
 #
 
 nums = (1..1000)