Question marks in regular expressions

Question

I\'m reading the regular expressions reference and I\'m thinking about ? and ?? characters. Could you explain me with some examples their usefulness? I don\'t understand the

Answer 1

? simply makes the previous item (character, character class, group) optional:

colou?r

matches "color" and "colour"

(swimming )?pool

matches "a pool" and "the swimming pool"

?? is the same, but it's also lazy, so the item will be excluded if at all possible. As those docs note, ?? is rare in practice. I have never used it.