My five year-old is intensely interested in what I do. How should I introduce him to programming?

My son seems to be advanced in mathematics (related to his peers) already computing fractions, doing long division, etc., and is very interested in "making computers go." He's five.

What do you think is the best way to introduce him to programming?

I am inclined to use a subset of a language to introduce him to control structures, etc., but I'm old, and that's how I was taught in the 80s. Are there better methods to introduce modern programming techniques to students -- and especially young students?

Thanks for any feedback.

EDIT: Thanks for all the comments! I have lots of resources and ideas now to help get him started.