Graham Sutherland / Polynomialprotip: ALWAYS use regular expression literals in JavaScript and TypeScript and any other language that supports it, instead of writing your regex out in a string. I cannot count how many critical security bugs I have found over the years from someone writing a regex like "^en\.wikipedia\.org$", which is incorrect because the \. is treated as *string* escape sequence (an invalid one that just produces .) which then results in the regex being "^en.wikipedia.org$" which matches "enowikipedia.org".
Freja@gsuberland similarly, use r"raw strings" instead of "normal strings" when using Python, to avoid similar bugs in regexes
(to be clear, in python, a string literal that starts with r" will not interpret any escape sequences but include each character exactly as typed into the string)