sub updateRecord {
  my ($srml_file,$n,$new) = @_;
  my ($offset, $data, $post);
  local $/;

  # no concurrent access, so no locking
  open CACHE, "+< $srml_file" or return setError($!);

  $/ = "<!-- START RECORD $n -->\n";
  <CACHE>;  # get up to the good stuff
  $offset = tell CACHE;

  $/ = "<!-- END RECORD $n -->\n";
  <CACHE>;  # waste what's there

  undef $/;
  $post = <CACHE>;  # get what's left

  seek CACHE, $offset, 0;
  truncate CACHE, $offset;  # in case new data is shorter

  print CACHE
    "<!-- START RECORD $n -->\n",
    getSRML($new),
    "<!-- END RECORD $n -->\n",
    $post;

  close CACHE;

  return -s $srml_file;
}