What he says is that programs contain two types of code, 'natural' code which actually describes and solves the problem in hand and 'synthetic' code which is only there as an artifact of the particular method that you have chosen to solve the problem. Examples of synthetic code are things like loop counters.
He goes on to say that a good program will minimise the amount of synthetic code as too much synthetic code will disguise the natural code and make the program harder to understand. Naturally he shows that Perl is very good at cutting down on the amount of synthetic code in a program.
It's a very interesting article and I'm recommend you all read it. If you're interested, the first of these articles can be found here.