Tim Bray did a test on Erlang, by using it to parse Apache’s log file and measure the performance. It did not work out. Tim gives a Ruby script which does what he is looking for. And others have then picked up on it, by doing it in their choice of language. Fredrik Lundh’s Python solution brings out a lot of gems that we can use to optimize Python code. Pete Kirkham gives his concise C++ code, using different algorithms. Even if not Erlang, it has brought out interesting code out for other languages.
Regarding Erlang, I wonder if it is a wrong choice for this problem. Erlang is high on concurrency, and lowers the barriers to run multiple processes. In fact its USP lies in building concurrent and distributed applications. I doubt it will be suitable for smaller tasks.