I must be misunderstanding something, but I don't know what you're suggesting I do to actually make my code work. How would I use that to make a replacement for my Perl Tidy utility?

I've been suggesting number 4 from Basic debugging checklist, examine the data with Data::Dumper/Data::Dump/JSON/YAML

I tried to reproduce your problem,

First I created a perl file written in unicode called foo.pl

Then I gave this file to perltidy, your perltidy, your perltidy with Dump ... in all versions the non-ascii characters survived unharmed :)

I also showed how cmd.exe can appear to show "corruption" of the file, but the actual bytes are as they should be

Text editors can show the same corruption by reading a utf-8 file as some other encoding

Either BBEdit is treating these bytes as something other than utf-8

Or Perl::Tidy is producing the wrong bytes

I think I've shown Perl::Tidy is doing its job without problems, what do you think?