note Dietz <code>5. Do know what your regex really means. • Do know about ^, $, variable interpolation, the matching rules as described by the Camel Book, modifiers, and the meaning of \n (newline) in combination with ., ^ and $</code> Do know about precedence since disregarding it is one of the highest crime in regex country: I've made a sample common mistake not paying attention to precedence and I use this as a chance to pillory myself giving a perfect example of what not to do. In node [id://382295] I was using an alternation being based on anchors: <code>/^0|6$/</code> This simply says match 0 at the beginning or match 6 at the end while my intention was to match 0 or 6 ranging from beginning to the end of the string: <code>/^(?:0|6)$/</code> As an addition to your tutorial I'd like to see the basic requirement for regexes: • You can't write an efficient regex as long as you don't know what your expected data will be: Always think of the expected data while changing or simplifying regexes. I personally like the term 'regexpected' Keep it in mind and it will save your life ;-) Please feel free to downvote node [id://382295] [Dietz|/me] castigating myself for not paying attention to precedence 383015 383015