I wrote this code so it must be perfect, no need to test it.
I remember my computer teacher in college emphasizing how to test your programming. At my part-time job one of my coworkers had to calculate many many many results from an experiment and since I was taking a computer class, I volunteered to write a class project program to do the figuring. So for the first real program (in Fortran) I wrote, there were five branching points, two of them within another branch, and I laboriously tested every combination of them at my desk by hand.
Perfect !
I submitted it to the school's IBM 1620 computer and it ran perfectly except for one thing. The computer folks said I should have used the line printer for printing instead of the console typewriter and it took a long time but they let it run since it was a class project and it was working correctly anyhow. They said it took about an hour with the console typewriter clickety clacking away.
"PRINT" instead of "LPRINT."
So there went "perfection" in my first real programming effort.
The IBM 1620, an early IBM "office" computer:
Formerly Perfect Terry, 230RN