*?,+?,?? 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.
+ "\\" 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.
(?#...) 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.
The special sequences consist of "\\" and a character from the list
below. If the ordinary character is not on the list, then the
subn Same as sub, but also return the number of substitutions made.
split Split a string by the occurrences of a pattern.
findall Find all occurrences of a pattern in a string.
+ finditer Return an iterator yielding a match object for each match.
compile Compile a pattern into a RegexObject.
purge Clear the regular expression cache.
escape Backslash all non-alphanumerics in a string.