Depends on your definition of "perfect" and "improved". Is it perfect because it does one fundamental thing really well? Is it improved by adding new features?

I think what you're meaning is, is there a program that is ubiquitous (or at least works anywhere), will basically remain used forever because it does a fundamental job that will always need to be done, and it does that job in the most straightforward way possible that can't be made any algorithmically simpler, faster, etc. Probably plenty, honestly. Bitwise operations, arithmetic, fetch/store, etc. Though ubiquity/working anywhere gets rarer the higher you go from hardware. Even your suggestion of cd, for example, has to interface with an OS's file system, of which there are several common types. What it's doing is simple in concept, but will always be dependent on other programs for the file system.