Overall, I was quite happy with the process. It was detailed and thorough enough, so I felt confident that they are doing a good job at picking good candidates only so I will not have to deal with ... suboptimal colleagues if I get hired and at the same time it was not tiring or boring.

There was a written test about Perl and a couple of rounds of interviews with prospective colleagues and managers, with enough time for both sides to ask questions. All people involved were friendly and felt really interested in the process.

Nothing really "unexpected". The most difficult question was to write a short program in Perl on a piece of paper.