I've been surprised at how often people convert long lists line-by-line. You can sometimes take what was a multiple-hour task and complete it with a handful of cryptic characters.
Reading the first chapter of ORiley's Mastering Regular Expressions was what made me get it and that was maybe an hours worth of time.
For example, I remember once replacing a buggy 3-4 lines of python based on split/etc with a single regex: match all \d+ (it was for extracting IDs from a user-input string)
John Smith > Smith, John Anna Peterson > Peterson, Anna
I can write:
(.) (.)
And replace with:
\2, \1
Not sure if that’s part of some “official” regex spec but it works more or less everywhere.
(Of course if it was an actual list of names I’d have to be a lot more intelligent with double names etc.)
Regular expression libraries then often can use these boundaries, for the whole match and for groups, for transform the string (e.g. replacing what was matched by a group with some other content).