For me, at least, the issues I raised have less to do with morality than practicality (sorry to all you upvoters who thought I was making a grand anti-censorship speech :-) Parsing the English language is an extremely difficult task to automate, regardless of your motive or objective.

Unless you are using key words that are unlikely to be used in conversation unrelated to what you're trying to capture, you'll end up with bogus results unless you can also analyze and interpret context. Even humans don't do so well at that -- hence the use of "magic words" like "mayday" or "I am declaring an emergency" instead of "help" in situations where it really matters.

Trying to code this sort of understanding into a perl regex without resorting to predefined magic words would be quite a trick. Automating action based on anything a perl regex could identify simply won't do you much good in the long run.