Under the functional programming paradigm, a program consists of a set of functions in the mathematical sense of the word.  The language ML that is used in Thomas VanDrunen's book is an example of a functional programming language.  Another -widely used- functional programming language is LISP.  LISP has a very simple syntax.  Here is an example of a simple LISP program

(defun mult_through_add (a, b)
     (if (eq a 0)
          b
          a + mult_through_add(a, b - 1)
     )
)

defun defines a new function and if is an in-built function in LISP which takes three arguments.  It evaluates the first argument and if it does not evaluate to false, it evaluates the second argument and otherwise it evaluates the third.  In other words, it is the if-then-else operator.  Clearly, the definition assumes that b is a positive number.

Once we have defined a function, we can either call it directly, or use it in the definition of another function.

Find out more details about LISP at

http://en.wikipedia.org/wiki/Lisp_%28programming_language%29

or

http://www.gigamonkeys.com/book/

and see an example of a larger LISP program at

http://www.csc.villanova.edu/~dmatusze/resources/lisp/lisp-example.html