class expressions are additional to
	  the square brackets delimiting a collection.  For example, the
	  following is a plausible pattern for a UNIX filename:
	  "[-./[:alnum:]_~]\+".  That is, a list of at least one character,
	  each of which is either '-', '.', '/', alphabetic, numeric, '_' or
	  '~'.
	  These items only work for 8-bit characters, except [:lower:] and
	  [:upper:] also work for multibyte characters when using the new
	  regexp engine.  See |two-engines|.  In the future these items may
	  work for multibyte characters.  For now, to get all "alpha"
	  characters you can use: [[:lower:][:upper:]].

	  The "Func" column shows what library function is used.  The
	  implementation depends on the system.  Otherwise:
	  (1) Uses islower() for ASCII and Vim builtin rules for other
	  characters.
	  (2) Uses Vim builtin rules
	  (3) As with (1) but using isupper()
							*/[[=* *[==]*
	- An equivalence class.  This means that characters are matched that
	  have almost the same meaning, e.g., when ignoring accents.  This
	  only works for Unicode, latin1 and latin9.  The form is:
		[=a=]
							*/[[.* *[..]*
	- A collation element.  This currently simply accepts a single
	  character in the form:
		[.a.]
							  */\]*
	- To include a literal ']', '^', '-' or '\' in the collection, put a
	  backslash before it: "[xyz\]]", "[\^xyz]", "[xy\-z]" and "[xyz\\]".
	  (Note: POSIX does not support the use of a backslash this way).  For
	  ']' you can also make it the first character (following a possible
	  "^"):  "[]xyz]" or "[^]xyz]".
	  For '-' you can also make it the first or last character: "[-xyz]",
	  "[^-xyz]" or "[xyz-]".  For '\' you can also let it be followed by
	  any character that's not in "^]-\bdertnoUux".  "[\xyz]" matches '\',
	  'x', 'y' and 'z'.  It's better to use "\\" though, future expansions
	  may use other characters after '\'.
	- Omitting the trailing ] is not considered an error.  "[]" works like
	  "[]]", it matches the ']' character.
	- The following translations are accepted when the 'l' flag is not
	  included in 'cpoptions':
		\e	<Esc>
		\t	<Tab>
		\r	<CR>	(NOT end-of-line!)
		\b	<BS>
		\n	line break, see above |/[\n]|
		\d123	decimal number of character
		\o40	octal number of character up to 0o377
		\x20	hexadecimal number of character up to 0xff
		\u20AC	hex. number of multibyte character up to 0xffff
		\U1234	hex. number of multibyte character up to 8 characters
			0xffffffff |E1541|
	  NOTE: The other backslash codes mentioned above do not work inside
	  []!
	- Matching with a collection can be slow, because each character in
	  the text has to be compared with each character in the collection.
	  Use one of the other atoms above when possible.  Example: "\d" is
	  much faster than "[0-9]" and matches the same characters.  However,
	  the new |NFA| regexp engine deals with this better than the old one.

						*/\%[]* *E69* *E70* *E369*
\%[]	A sequence of optionally matched atoms.  This always matches.
	It matches as much of the list of atoms it contains as possible.  Thus
	it stops at the first atom that doesn't match.  For example: >
		/r\%[ead]
<	matches "r", "re", "rea" or "read".  The longest that matches is used.
	To match the Ex command "function", where "fu" is required and
	"nction" is optional, this would work: >
		/\<fu\%[nction]\>
<	The end-of-word atom "\>" is used to avoid matching "fu" in "full".
	It gets more complicated when the atoms are not ordinary characters.
	You don't often have to use it, but it is possible.  Example: >
		/\<r\%[[eo]ad]\>
<	Matches the words "r", "re", "ro", "rea", "roa", "read" and "road".
	There can be no \(\), \%(\) or \z(\) items inside the [] and \%[] does
	not nest.
	To include a "[" use "[[]" and for "]" use []]", e.g.,: >
		/index\%[[[]0[]]]
<	matches "index" "index[", "index[0" and "index[0]".

				*/\%d* */\%x* */\%o* */\%u* */\%U* *E678*

\%d123	Matches the character specified with a decimal number.  Must be
	followed by a non-digit.
\%o40