One of my favorite interview questions is from Steve Yegge. Ask the candidate to explain how they would change the format of phone numbers in thousands of files.
It’s a question that screams, “Use Perl” or “Use Unix”, but you’d be surprised just how few people get it right.
The C#/Java’s developer answer is to write a program that reads in a program line by line, and parses out each string using built in string manipulation. The smarter C#/Java developers even say to do that, but use a Regular Expression instead of built in string manipulation.
That’s all well and good, but it misses the point of the exercise: Don’t fight your platform, Use the right tool for the right job.