keyword() {
    var captures
      , tok;
    if (captures = /^(return|if|else|unless|for|in)\b(?!-)[ \t]*/.exec(this.str)) {
      var keyword = captures[1];
      this.skip(captures);
      if (this.isPartOfSelector()) {
        tok = new Token('ident', new nodes.Ident(captures[0]));
      } else {
        tok = new Token(keyword, keyword);
      }
      return tok;
    }
  }
'if'
| 'else'
| 'unless'
| 'return'
| 'for'
| 'in'