I can't believe it's a good job: most of what I read in erlang is the OTP source. There are some real stinkers in there, in modules that barely anyone uses anymore (so there aren't any bug reports), like tftp (but when you need it you need it). And if you've ever tried chasing the ssl code, there's definitely some java-esque factory patterns hiding in there where one module or another drops an interface back to its caller, and the call stack weaves several times between two or three modules even.