Reference: https://pubs.opengroup.org/onlinepubs/9799919799/basedefs/V1_chap09.html section 6.4.6:
"Each of the duplication symbols ('+', '*', '?', and intervals) can be suffixed by the repetition modifier '?' (), in which case matching behavior for that repetition shall be changed from the leftmost longest possible match to the leftmost shortest possible match, including the null match."
Reference: https://pubs.opengroup.org/onlinepubs/9799919799/basedefs/V1_chap09.html section 6.4.6: "Each of the duplication symbols ('+', '*', '?', and intervals) can be suffixed by the repetition modifier '?' (), in which case matching behavior for that repetition shall be changed from the leftmost longest possible match to the leftmost shortest possible match, including the null match."