Regular expression literals may include an optional modifier to control different aspects of matching. The modifiers are specified as an optional flag. You can provide multiple modifiers using exclusive OR (|), and may be represented by one of these −
The following is a list of different re modifiers and their functions.
Performs case-insensitive matching.
Interprets words according to the current locale. This interpretation affects the alphabetic group (\w and \W), as well as word boundary behavior(\b and \B).
Makes $ match the end of a line (not just the end of the string) and makes ^ match the start of any line (not just the start of the string).
Makes a period (dot) match any character, including a newline.
Interprets letters according to the Unicode character set. This flag affects the behavior of \w, \W, \b, \B.
Permits "cuter" regular expression syntax. It ignores whitespace (except inside a set  or when escaped by a backslash) and treats unescaped # as a comment marker.