page 391, second to last paragraph : discrepancy warn
<-> $stderr.puts
There’s an important subtlety in this code. The body of the log method contains this line:
warn("#{now}-#{id_string}: #{self} (#{msg})")
But the body of the log method in metaprogramming/logging_2.rb
contains :
$stderr.puts("#{now}-#{id_string}: #{self} (#{msg})")
That said, the output is the same.