Regular expressions

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

a for character a, for any a (special characters need escaping).
\n for the new line character (Unicode U+0A).
\r for the carriage return character (Unicode U+0D).
\t for the tab character (Unicode U+09).
\a for character a, for any a (especially useful for escaping special characters).
\\ for character \ (escaped).
\" for character " (escaped).
(x) for regular expression x (allows for grouping).
xy for regular expression x followed by regular expression y.
x* for zero or more times regular expression x.
x+ for one or more times regular expression x.
x? for zero or one times regular expression x.
. for any ASCII character except \n (new line, Unicode U+0A).
x|y for either regular expression x or regular expression y (but not both).
[abc] for exactly one of the characters a, b or c.
[a-z] for exactly one of the characters a, b, …, or z. This notation is called a character class. Note that the ranges of characters are based on their ASCII character codes.
[^a] for any ASCII character except for character a. This notation is called a negated character class.
{s} for the regular expression defined by shortcut s.

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.