Regex Brazilian postal code (CEP)

A Brazilian CEP is 8 digits, written '00000-000' with a hyphen after the fifth. But nobody always types the hyphen, and real attempts split into two camps that each get it wrong in one direction: the widely used GeoNames file requires it and rejects '01001000'; a Google libaddressinput rule tolerates it but never anchors the pattern, so 'CEP 01001-000' or 'abc01001000xyz' pass. A Crystal library even has to split this into two regexes, one with the hyphen and one without. Here's an anchored pattern accepting both spellings, compared against those three real attempts.