sub filter_and_return_ref($) {
  my($fn) = @_;
  open my $f, '<', $fn or return;
  local $/;
  local $_ = <$f>;
  s/\A/{ /;
  s/\Z/ }/;
  s/(\S+)\n/ => "$1",\n/g;
  my $r = eval $_;
  return if $@;
  $r || {}
}