docs: function(){
      var captures;
      if (captures = /^mixin +([-\w]+)(?: *\((.*)\))? */.exec(this.input)) {
        this.consume(captures[0].length);
        var tok = this.tok('mixin', captures[1]);
        tok.args = captures[2] || null;
        this.tokens.push(tok);
        return true;
      }
    }