A cheat sheet about regular expressions used in Sublime Text.

Special characters
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expression	Description
`.`	Match any character
`^`	Match line begin
`$`	Match line end
`*`	Match previous RE 0 or more times greedily
`*?`	Match previous RE 0 or more times non-greedily
`+`	Match previous RE 1 or more times greedily
`+?`	Match previous RE 1 or more times non-greedily
`?`	Match previous RE 0 or 1 time greedily
`??`	Match previous RE 0 or 1 time non-greedily
`A\|B`	Match either RE A or B
`{m}`	Match previous RE exactly m times
`{m,n}`	Match previous RE m to n times greedily
`{m, n}?`	Match previous RE m to n times, non-greedily

Character set
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expression	Description
`[abc]`	Match either `a`, `b` or `c`
`[^abc]`	Match any character not in this set (i.e., not `a`, `b` and `c`)
`[a-z]`	Match the range from `a` to `z`
`[a-f2-8]`	Match the range from `a` to `f` or the range from `2` to `8`
`[a\-z]`	Match `a`, `-` or `z`
`[a-]`	Match `a`, `-`
`[-a]`	Match `-`, `a`
`[{}*\|()[]+\^$.?]`	Match either one of the chacters in `[]{}*\|()+^$?.`

Note that you can also use character class inside [], for example, [\w] matches any character in word character class.

An expression of the form [[:name:]] matches the named character class name.

class name	Description
`alnum`	Any alpha-numeric character
`alpha`	Any alphabetic character.
`digit`	Any decimal digit.
`xdigit`	Any hexadecimal digit character.
`lower`	Any lower case character.
`upper`	Any upper case character.
`cntrl`	Any control character¹.
`print`	Any printable character.
`punct`	Any punctuation character. ²
`space`	Any whitespace character. ³
`word`	Any word character (alphanumeric characters plus the underscore).

Note: To use upper and lower, you have to enable case sensitve search.

expression	Description
`(?<NAME>pattern)`	Define a regex group named `NAME` which you can later refer to with `\g{NAME}`
`(?=pattern)`	Positive lookahead, consumes zero characters, the preceding RE only matches if this matches
`(?!pattern)`	Negative lookahead, consumes zero characters, the preceding RE only matches if this does not match
`(?<=pattern)`	Positive lookbehind, consumes zero characters, the following RE will only match if preceded with this fixed length RE.
`(?<!pattern)`	Negative lookbehind, consumes zero characters, the following RE will only match if not preceded with this fixed length RE.

expression	Description
`\1`	Refer to first regex group
`\g{1}`	Refer to first regex group
`\g{12}`	Refer to 12th regex group
`\g{-1}`	Refer to last regex group
`\g{-2}`	Refer to last but one regex group

The regex groups are indexed by the order of their opening braces.
Note the \g{NUM} form allows for matching regex group index larger than 9, for example, \g{12}.

class name	Description
`\xdd`	A hexadecimal escape sequence - matches the single character whose code point is `0xdd`.
`\x{dddd}`	A hexadecimal escape sequence - matches the single character whose code point is `0xdddd`.

The following escape sequences match the boundaries of words:

class name	Description
`\<`	Matches the start of a word.
`\>`	Matches the end of a word.
`\b`	Matches a word boundary (the start or end of a word).
`\B`	Matches only when not at a word boundary.