(Prism.languages.bnf = {
  string: { pattern: /"[^\r\n"]*"|'[^\r\n']*'/ },
  definition: {
    pattern: /<[^<>\r\n\t]+>(?=\s*::=)/,
    alias: ['rule', 'keyword'],
    inside: { punctuation: /^<|>$/ },
  },
  rule: { pattern: /<[^<>\r\n\t]+>/, inside: { punctuation: /^<|>$/ } },
  operator: /::=|[|()[\]{}*+?]|\.{3}/,
}),
  (Prism.languages.rbnf = Prism.languages.bnf);