On Thu, Aug 5, 2021 at 11:22 AM Ray Andrews <rayandrews@xxxxxxxxxxx> wrote: > > So it's ' [: ' that should be taken as > a single entity and ':] ' likewise. Uh, no. Inside a [...] character class, the entire sequence [:word:] is a single entity, for certain values of word. Outside of a character class, [: and :] have no special meaning.