Basic regular expression construct

Regular expressions are made up of two types of characters: normal text characters, called literals, and special characters, such as the asterisk (*, +, ?, .), called metacharacters. There are times when you want to match a metacharacter as a literal character. In such cases, we prefix that metacharacter with a backslash (\), which is called an escape sequence.

The basic regular expression construct can be summarized as follows:

Here is the list of metacharacters, also known as special characters, that are used in building regular expressions:

\    ^    $    .    [    ]    |    (    )    *    +    ?

The following table lists the remaining elements that are used in building a basic regular expression, apart from the metacharacters mentioned before:

Literal	A literal character (non-metacharacter ), such as A, that matches itself.
Escape sequence	An escape sequence that matches a special symbol: for example \t matches tab.
Quoted metacharacter (\)	In quoted metacharacters...