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;