code: function parseMultiline(ln, prefix) {
      var s = "";
      for (;;) {
          if (prefix)
              putstr(prefix);
          var more = readline();
          if (more === null)
              return null;
          // the only command recognized in multiline mode is .end
          if (more.match(/^[\s]*\.end[\s]*$/))
              break;
          s += "\n" + more;
      }
      var t = new Tokenizer(s, "stdin", ln.value, false);
      var p = new Parser(t);
      var n = p.Script(false, false);
      ln.value = t.lineno;
      return n;
  }
docs: /*
  parseMultiline :: ({line number}, string | null) -> program node