Conal Elliott wrote on his blog that C is really a pure functional language called cpp that can be reduced to a monadic construct called C. Fortunately for us, there is alot of prior knowledge in reducing C into highly optimized machine code.
I would like to add that Make is also a pure functional language. It is a set of rules that can be reduced to a set of shell scripts, which unfortunately do not share the same optimizations. Fortunately, shell scripting lets you insert code in the form of a variable with some amazing metaprogramming consequences.
If you're on the fence about FP, it's really more pervasive than that silly academic language, Haskell.