+use_ok 'PublicInbox::Hval', qw(to_attr);
+
+# reverse the result of to_attr
+sub from_attr ($) {
+ my ($str) = @_;
+ my $first = '';
+ if ($str =~ s/\AZ([a-f0-9]{2})//ms) {
+ $first = chr(hex($1));
+ }
+ $str =~ s!::([a-f0-9]{2})!chr(hex($1))!egms;
+ $str =~ tr!:!/!;
+ utf8::decode($str);
+ $first . $str;
+}