The log can be output in a compressed form using gzip or bzip2 (-G or -B flags)
The event log is a lossless format that will let you completely replay a test run (or parts of it) without actually re-running your tests.
The event log has Test2 events, with all their context data, in most cases there was no TAP conversion involved.
stdout/stderr exit codes, and all other data the harness collects are placed into events in the log.
There are several tools to process logs and provide useful metrics or summarize results.
Here we ask it to only output from one of the failures.
Now we will ask it for the verbose version of the output
This command will load a log file into a PostgreSQL database and launch a web-app that lets you view the run in detail.
Assuming you are watching this presentation and not simply reading my slides, I will now demonstrate the command.
For anyone reading the slides, here is a screenshot for your trouble: