algorithm to try next should be merge insertion. See Knuth section
5.3.1, who credits Lester Ford, Jr. and Selmer Johnson, American
Mathematical Monthly 66 (1959), 387-389.
+
+Document the exit status of each and every program.
+ Suggestion from Dan Jacobson.
+ The sentence or two describing the common case must appear just once,
+ and then it must be made to appear in the 70+ places where it's needed.