[asQuirreL]

This is a false dichotomy -- regexes and parsers both have their place, even when solving the same problem.

The troubles start when you try and solve the whole thing in one step, using just regular expressions, or parsers.

Regular expressions are good at tokenizing input (converting a stream of bytes into a stream of other things, e.g. picking out numbers, punctuation, keywords).

Parsers are good at identifying structure in a token stream.

Neither are good at evaluation. Leave that as its own step.

Applying this rule to the example in the article (Advent of Code 2024 Day 3), I would still use regular expressions to identify mul(\d+,\d+), do(), and don't(), I don't think I need a parser because there is no extra structure beyond that token stream, and I would leave it up to the evaluator to track the state of whether multiplication is enabled or not.