found is used:
- The keyword currently under the cursor.
- The first keyword to the right of the cursor, in the same line.
- The WORD currently under the cursor.
- The first WORD to the right of the cursor, in the same line.
The keyword may only contain letters and characters in 'iskeyword'.
The WORD may contain any non-blanks (<Tab>s and/or <Space>s).
Note that if you type with ten fingers, the characters are easy to remember:
the "#" is under your left hand middle finger (search to the left and up) and
the "*" is under your right hand middle finger (search to the right and down).
(this depends on your keyboard layout though).

								*E956*
In very rare cases a regular expression is used recursively.  This can happen
when executing a pattern takes a long time and when checking for messages on
channels a callback is invoked that also uses a pattern or an autocommand is
triggered.  In most cases this should be fine, but if a pattern is in use when
it's used again it fails.  Usually this means there is something wrong with
the pattern.

==============================================================================
2. The definition of a pattern		*search-pattern* *pattern* *[pattern]*
					*regular-expression* *regexp* *Pattern*
					*E383* *E476*

For starters, read chapter 27 of the user manual |usr_27.txt|.

						*/bar* */\bar* */pattern*
1. A pattern is one or more branches, separated by "\|".  It matches anything
   that matches one of the branches.  Example: "foo\|beep" matches "foo" and
   matches "beep".  If more than one branch matches, the first one is used.

   pattern ::=	    branch
		or  branch \| branch
		or  branch \| branch \| branch
		etc.

						*/branch* */\&*
2. A branch is one or more concats, separated by "\&".  It matches the last
   concat, but only if all the preceding concats also match at the same
   position.  Examples:
	"foobeep\&..." matches "foo" in "foobeep".
	".*Peter\&.*Bob" matches in a line containing both "Peter" and "Bob"

   branch ::=	    concat
		or  concat \& concat
		or  concat \& concat \& concat
		etc.

						*/concat*
3. A concat is one or more pieces, concatenated.  It matches a match for the
   first piece, followed by a match for the second piece, etc.  Example:
   "f[0-9]b", first matches "f", then a digit and then "b".

   concat  ::=	    piece
		or  piece piece
		or  piece piece piece
		etc.

						*/piece*
4. A piece is an atom, possibly followed by a multi, an indication of how many
   times the atom can be matched.  Example: "a*" matches any sequence of "a"
   characters: "", "a", "aa", etc.  See |/multi|.

   piece   ::=	    atom
		or  atom  multi

						*/atom*
5. An atom can be one of a long list of items.  Many atoms match one character
   in the text.  It is often an ordinary character or a character class.
   Parentheses can be used to make a pattern into an atom.  The "\z(\)"
   construct is only for syntax highlighting.

   atom    ::=	    ordinary-atom		|/ordinary-atom|
		or  \( pattern \)		|/\(|
		or  \%( pattern \)		|/\%(|
		or  \z( pattern \)		|/\z(|


				*/\%#=* *two-engines* *NFA*
Vim includes two regexp engines:
1. An old, backtracking engine that supports everything.
2. A new, NFA engine that works much faster on some patterns, possibly slower
   on some patterns.
								 *E1281*
Vim will automatically select the right engine for you.  However, if you run
into a problem or want to specifically select one engine or the other, you can
prepend one of the following to the pattern:

	\%#=0	Force automatic selection.  Only has an effect when
		'regexpengine' has been set to a non-zero value.
	\%#=1	Force using the old engine.
	\%#=2	Force using the NFA engine.

You can also use the 'regexpengine' option to change the default.

			 *E864* *E868* *E874* *E875* *E876* *E877* *E878*
If selecting the NFA engine and it runs into something that is not implemented
the pattern will not match.  This is only useful when debugging Vim.

==============================================================================