Note that the apparently similar pattern (?!foo)bar does not find an occurrence of "bar "that is preceded by something other than "foo"; it finds any occurrence of "bar" whatsoever, because the assertion (?!foo) is always TRUE Note that the apparently similar pattern (?!foo)bar does not find an occurrence of "bar "that is preceded by something other than "foo"; it finds any occurrence of "bar" whatsoever, because the assertion (?!foo) is always TRUE when the next three characters are "bar ".
Une assertion arrière est ici nécessaire.