\ Escapes a character that has a special meaning. Thus, \. means a literal . character. Additionally, placing \ in front of a regular character can add a special meaning to that character. For example, \t indicates a tab character.

^ An anchor that insists the pattern start at the beginning of the string. ^A means that the string must start with A.

$ An anchor that insists the string end with the specified pattern. X$ means that the string must end with X.

+ Matches the previous construct one or more times. For example, a+ means "one or more 'a's."

* Matches the previous construct zero or more times. This is the same as +, except that it's also acceptable if the thing wasn't there at all.

( ) Provides grouping and capturing functions. Grouping means treating two or more characters as though they were a single unit. Capturing means remembering the thing that matched, so that we can use it again later. This is called a backreference.

| = Or (backslashed | is a literal pipe)

? Matches the previous construct zero or one times. In other words, make it optional. It also makes the * and + characters "non-greedy." Everything in parens ended by a ? is optional.

[:punct:] - match all punctuation.

[:blank:] - match character space and tab

.* - match anything