No you got that right. Be unsure no longer. The named POSIX classes are nice for keeping things clear especially when you consider character sets and Unicode. [A-Za-z0-9_] is sufficient for US-ASCII but it's wordy and easier to mistype than [:alphanum:]. The nice thing is that if you start moving beyond US-ASCII then you've already taken care of some of th work up front. It's also more in line with what I gather will be the expected idiom for perl6. The idea here is that it is infeasable for you to actually specify what is a "word" character for whatever character set you're using in your regular expression.