tl;dr:"When interviewing programmers, I often ask them to code a simple program to count word frequencies in a text file. It’s a good problem that tests a bunch of skills, and with some follow-up questions, allows you to go surprisingly deep. One of the follow-up questions I ask is, “What’s the performance bottleneck in your program?” Most people say something like “reading from the input file”." Ben discusses why that's not usually the case.
tl;dr:"Back in 1998, Rob Pike – of Go and Plan 9 fame – wrote a simple regular expression matcher in C for The Practice of Programming... With Go’s C heritage, and Pike’s influence on the Go language, I thought I’d see how well the C code would translate to Go, and whether it was still elegant.