Regular expressions

Regular expressions are enclosed in double quotes. Within them, the following are supported:

To include special characters, they must always be escaped, wherever they occur in the regular expression. For instance, regular expression [a\^] recognizes either character a or character ^ (but not both). Here the ^ character is escaped, as it is a special character (it may be used at the beginning of a character class to invert the character class).

New lines are not allowed in the regular expressions themselves. Obviously, it is possible to detect new lines using regular expressions.