When this is the case, they match immediately after and immediately before an internal "\n" character, respectively, in additionWhen this is the case, they match immediately after and immediately before an internal "\n "character, respectively, in addition to matching at the start and end of the subject string.
La signification de $peut changer, de manière à l'amener à ce qu'il ne puisse se trouver qu 'en toute fin de la chaîne sujet.