Quel est le nom du jeton '\%' et '\ @' dans vim regex? Et que fait-il?

Lors de l'édition du fichier de syntaxe, j'ai trouvé quelque chose comme:

\s*\%(\%(:\@<!\/\/.*\)\=\|\%(\/\*.*\*\/\s*\)*\)$

Je ne connais personne d'autre que là \%- \@bas. Je ne peux même pas googler parce que je ne sais pas quel est son nom. Alors qu'est-ce que c'est et que fait-il?

Avant de googler, essayez le doc:

De :h \%

\%(\)   A pattern enclosed by escaped parentheses.
    Just like \(\), but without counting it as a sub-expression.  This
    allows using more groups and it's a little bit faster.
    {not in Vi}

Et :h \@<!

\@<!    Matches with zero width if the preceding atom does NOT match just
    before what follows.  Thus this matches if there is no position in the
    current or previous line where the atom matches such that it ends just
    before what follows.

    Like "(?<!pattern)" in Perl, but Vim allows non-fixed-width patterns.
    The match with the preceding atom is made to end just before the match
    with what follows, thus an atom that ends in ".*" will work.
    Warning: This can be slow (because many positions need to be checked
    for a match).  Use a limit if you can, see below.

    Example         matches ~

    \(foo\)\@<!bar      any "bar" that's not in "foobar"

    \(\/\/.*\)\@<!in    "in" which is not after "//"