Some people work in fields where there's an extremely high cost to making mistakes, and whose customers trust them to be careful and meticulous. Those people are paid to be more careful than your average code monkey who churns out regular expressions to save time instead of carefully researching the problem, performing code reviews, and using standard well tested libraries to parse complex but precisely documented standards like html and urls. Developing a browser plug-in to manage passwords is one of them.
Some people, when confronted with a problem, think "I know, I'll use regular expressions." Now they have two problems. -JWZ