The first computer I ever used was an HP 2100. Now after 40 years of working, mostly in mainframes, I work for HP. Circles. Many times I have given away a bit of JCL, code, script, whatever. Some distant recipient comes back to me. "I have a problem with your ...". I always say "Did you change it?". "...yes." Then I say "Let us fix YOUR ...". When I have mede the changes, I know what I changed. When you make the change, change carefully and test each change. Saving is like voting. Save early, save often.