README.md in dead_end-3.0.0 vs README.md in dead_end-3.0.1

@@ -168,10 +168,30 @@
 ### How to debug changes to output display
 
 You can see changes to output against a variety of invalid code by running specs and using the `DEBUG_DISPLAY=1` environment variable. For example:
 
 ```
-$ DEBUG_DISPLAY=1 be rspec spec/ --format=failures
+$ DEBUG_DISPLAY=1 bundle exec rspec spec/ --format=failures
+```
+
+### Run profiler
+
+You can output profiler data to the `tmp` directory by running:
+
+```
+$ DEBUG_PERF=1 bundle exec rspec spec/integration/dead_end_spec.rb
+```
+
+Some outputs are in text format, some are html, the raw marshaled data is available in `raw.rb.marshal`. See https://ruby-prof.github.io/#reports for more info. One interesting one, is the "kcachegrind" interface. To view this on mac:
+
+```
+$ brew install qcachegrind
+```
+
+Open:
+
+```
+$ qcachegrind tmp/last/profile.callgrind.out.<numbers>
 ```
 
 ## Contributing
 
 Bug reports and pull requests are welcome on GitHub at https://github.com/zombocom/dead_end. This project is intended to be a safe, welcoming space for collaboration, and contributors are expected to adhere to the [code of conduct](https://github.com/zombocom/dead_end/blob/master/CODE_OF_CONDUCT.md).