I'm surprised no one here's quoted... well, I don't know which guru said it, but it sure as heck wasn't me. The idea is that a single-use program that takes ten minutes to write and one second to execute is less 'efficient' in the global sense than one that takes one minute to write and ten seconds to execute.

Remember Mark Jason Dominus's #11908: "Premature optimization is the root of all evil."

To a large extent, worrying about efficiency when you're not doing a pimp-load of IO, or scads of numerical computation, is wasted effort. Factor in the time you, the coder, spend making the program, and you'll get a much better idea of the efficiency. Consider the global system.