http://l3tczdiiwoo63iwxty4lhs6p7eaxop5micbn7vbliydgv63x5zrrrfyd.onion/4.0.0/user-manual/appendix.html
"a" , "A" , "4" , ":" , or "@" . ? - The preceding character or expression is
matched ZERO or ONE times. Either/or. + - The preceding character or expression is
matched ONE or MORE times. * - The preceding character or expression is
matched ZERO or MORE times. \ - The "escape" character denotes that the following character should be taken literally.