I have not read all/most of the replies.

What material benefit does Haskell derive from being a "pure" functional language as opposed to an impure one? Please provide examples as I require instruction. A pure functional lanugage allows lazy evaluation, which adds another tool to your modularity toolbox, since it separates control from computation.

In a pure functional language state is very carefully isolated from the rest of your program. This makes all sorts of optimizations trivial that are very hard to do in other languages. Optimizations are done in "code algebra", which is very easy to do in Haskell (for pure functions), for example optimizations are harder to do in the "code algebra" of Java. For a better discussion of "code algbra" please see the following book: "Practical Formal Software Engineering: Wanting the Software You Get" Bruce Mills, 2009 -- Regards, Casey