By default, search commands perform @dfn{lax space matching}:
each space, or sequence of spaces, matches any sequence of one or more
whitespace characters in the text. (Incremental regexp search has a
-separate default; see @ref{Regexp Search}.) Hence, @samp{foo bar}
-matches @samp{foo bar}, @samp{foo@w{ }bar}, @samp{foo@w{ }bar}, and
-so on (but not @samp{foobar}). More precisely, Emacs matches each
-sequence of space characters in the search string to a regular
-expression specified by the variable @code{search-whitespace-regexp}.
-For example, to make spaces match sequences of newlines as well as
-spaces, set it to @samp{"[[:space:]\n]+"}. The default value of this
-variable depends on the buffer's major mode; most major modes classify
-spaces, tabs, and formfeed characters as whitespace.
+separate default; see @ref{Regexp Search}.) Hence, @w{@samp{foo bar}}
+matches @w{@samp{foo bar}}, @w{@samp{foo@ @ bar}},
+@w{@samp{foo@ @ @ bar}}, and so on (but not @samp{foobar}). More
+precisely, Emacs matches each sequence of space characters in the
+search string to a regular expression specified by the variable
+@code{search-whitespace-regexp}. For example, to make spaces match
+sequences of newlines as well as spaces, set it to
+@samp{"[[:space:]\n]+"}. The default value of this variable depends
+on the buffer's major mode; most major modes classify spaces, tabs,
+and formfeed characters as whitespace.
If you want whitespace characters to match exactly, you can turn lax
space matching off by typing @kbd{M-s @key{SPC}}