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CharactersMeans“.”Matches any character except a newline.“^”Matches the start of the string.“$”Matches the end of the string or just before the newline at the end of the string.“*”Matches 0 or more (greedy) repetitions of the preceding RE. Greedy means that it will match as many repetitions as possible.“+”Matches 1 or more (greedy) repetitions of the preceding RE.“?”Matches 0 or 1 (greedy) of the preceding RE.*?,+?,??Non-greedy versions of the previous three special characters.{m,n}Matches from m to n repetitions of the preceding RE.{m,n}?Non-greedy version of the above.“\”Either escapes special characters or signals a special sequence.[]Indicates a set of characters. A “^” as the first character indicates a complementing set.“|”A|B, creates an RE that will match either A or B.(…)Matches the RE inside the parentheses. The contents can be retrieved or matched later in the string.(?aiLmsux)Set the A, I, L, M, S, U, or X flag for the RE (see below).(?:…)Non-grouping version of regular parentheses.(?P…)The substring matched by the group is accessible by name.(?P=name)Matches the text matched earlier by the group named name.(?#…)A comment; ignored.(?=…)Matches if … matches next, but doesn’t consume the string.(?!…)Matches if … doesn’t match next.(?<=…)Matches if preceded by … (must be fixed length).(?Matches if not preceded by … (must be fixed length).(?(id/name)yes|no)Matches yes pattern if the group with id/name matched, the (optional) no pattern otherwise.