this isn’t just an academic curiosity. flip the alternation order to (ab|a)+ and suddenly PCRE matches the entire string! the | operator in backtracking engines is ordered - it’s not union, it’s “try left first”. the order of branches changes the result, which means | is not commutative. a|b and b|a can give different matches.
Студенты нашли останки викингов в яме для наказаний14:52
，这一点在体育直播中也有详细论述
To “show” the credential to some Resource, the user simply needs to hand over the pair (SN, signature). Assuming the Resource knows the public key (PK) of the issuer, it can simply verify that (1) the signature is valid on SN, and (2) nobody has every used that value SN in some previous credential “show”.
В двух аэропортах на юге России ввели ограничения на полеты14:55
食物價格飆升，越來越多伊朗人表示餐桌上紅肉消失，改以雞肉、起司或豆類等較便宜選項替代。