I think it goes beyond the original question now. :) If one wants to do proper thing, then definitely contractions, word variations, etc should be considered.

I think it goes beyond the original question now. :) If one wants to do proper thing, then definitely contractions, word variations, etc should be considered. For this, I guess something like OpenNLP can be used. What's interesting though is how UNIX shell, being essentially a symbolic FP language, allows one to solve the problem in a clear and concise way. And if one desires, the program can be easily modified to read sentences, say, from network from ssh tunneled via HTTPS. That kind of flexibility can rarely be achieved in languages like C# with tight coupling between the units of abstraction.