Hm. Long ago in my Mech.Eng. days, I spent 4 hours setting up a radial grinder to radius the egde of a push-fit spigot. The instructor watched from the other side of the shop until I got everything perfect and was putting my safety glasses on before coming over. Without saying a word he took the spigot out of the chuck, thereby complete screwing all the set-up work I'd done. I nearly had apoplexy.

He then walked over to a bench, mounted it in a standard vice, picked up a fine file and radiused the edge with about six gentle strokes of the file. Job done.

The lesson was that it was the taper on the spigot that required +0-0.0004" accuracy. The radius on the end is simply to stop it from binding in the hole.

Expend your time wisely, and choose tools that are fit for purpose. Filtering a subset of line records from a text file is a bread&butter, simple Perl problem, regardless of whether it contains last week football scores or top-secret NBC Bio data.