e — Evaluate replacement i — Perform case-insensitive matching g — Perform global matching m — Perform multiple line matching s — Treat strings as single line x — Allow comments and whitespace in pattern U — Non Greedy pattern

[abc] Find any of the characters between the brackets [^abc] Find any character not in the brackets [0-9] Used to find any digit from 0 to 9 [A-z] Find any character from uppercase A to lowercase z (a|b|c) Find any of the alternatives separated with |

. — Find a single character, except newline or line terminator \w — Word character \W — Non-word character \d — A digit \D — A non-digit character \s — Whitespace character \S — Non-whitespace character \b — Find a match at the beginning/end of a word \B — A match not at the beginning/end of a word \0 — NUL character \n — A new line character \f — Form feed character \r — Carriage return character \t — Tab character \v — Vertical tab character \xxx — The character specified by an octal number xxx \xdd — Character specified by a hexadecimal number dd \uxxxx — The Unicode character specified by a hexadecimal number xxxx

n+ — Matches any string that contains at least one n n* — Any string that contains zero or more occurrences of n n? — A string that contains zero or one occurrences of n n{X} — String that contains a sequence of X n’s n{X,Y} — Strings that contains a sequence of X to Y n’s n{X,} — Matches any string that contains a sequence of at least X n’s n$ — Any string with n at the end of it ^n — String with n at the beginning of it ?=n — Any string that is followed by a specific string n ?!n — String that is not followed by a specific string n