$ perl -E 'mkdir("\x{100}")'
$ perl -MB -E 'my @d= <*>; say B::perlstring($_) for @d'
"\304\200"
$ perl -E 'my ($d)= <*>; open(my $f, ">", "$d/\x{101}.txt") or die "$!"'
No such file or directory at -e line 1.

##</code><code>##

$ python2.7
Python 2.7.18 (default, Oct 10 2021, 22:29:32) 
[GCC 11.1.0] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> import os
>>> l=os.listdir(".")
>>> l
['\xc4\x80']
>>> l=os.listdir(u".")
>>> l
[u'\u0100']

##</code><code>##

$ perl -MB -E 'open(my $f, ">", "\x{C4}\x{80}\x{A0}.txt") or die "$!"'
$ python2.7
Python 2.7.18 (default, Oct 10 2021, 22:29:32) 
[GCC 11.1.0] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> import os
>>> l=os.listdir('.')
>>> l
['\xc4\x80\xa0.txt', '\xc4\x80']
>>> l=os.listdir(u'.')
>>> l
['\xc4\x80\xa0.txt', u'\u0100']

##</code><code>##

>>> open(l[1]+'/'+l[0], 'w')
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
UnicodeDecodeError: 'ascii' codec can't decode byte 0xc4 in position 0: ordinal not in range(128)

##</code><code>##

$ python3
Python 3.11.3 (main, Jun  5 2023, 09:32:32) [GCC 13.1.1 20230429] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import os
>>> l=os.listdir('.')
>>> l
['&#256;\udca0.txt', '&#256;']
>>> 

##</code><code>##

>>> open(l[1]+'/'+l[0], "w")
<_io.TextIOWrapper name='&#256;/&#256;\udca0.txt' mode='w' encoding='UTF-8'>
>>> l=os.listdir('\u0100')
>>> l
['&#256;\udca0.txt']
^d

$ perl -E '
sub escapestr {
  $_[0] =~ s/([^\x20-\x7E])/sprintf("\\x%02X", ord $1)/egr
}
say escapestr($_) for <\x{100}/*>'

\xC4\x80/\xC4\x80\xA0.txt

##</code><code>##

use feature 'unicodefilenames';
my ($d)= <*>;
open(my $f, ">", "$d/\x{101}.txt") or die "$!";

##</code><code>##

package New;
use v5.42;
use feature 'unicodefilenames';

Old->foo($_) for <*>;

package Old;
use v5.38;

sub foo($fname) {
  open my $fh, "<", $fname;
}

##</code><code>##

package New;
use v5.42;
use feature 'unicodefilenames';

Old->foo($_) for <*>;

package Old;
use v5.38;

sub foo($fname) {
  my $dir= "tmp\x{85}";
  mkdir $dir or die "$!";
  system("cp -a $fname $dir/$fname") == 0 or die "$!";
}

##</code><code>##

$ python3
Python 3.11.3 (main, Jun  5 2023, 09:32:32) [GCC 13.1.1 20230429] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import subprocess
(Wrapped for readability)
>>> subprocess.run([
  'perl','-E',
  'sub escapestr {
      $_[0] =~ s/([^\x20-\x7E])/sprintf("\\x%02X", ord $1)/egr
   }
   say escapestr($ARGV[0])',
   "\x80"])
C280
>>> subprocess.run([
  'perl','-E',
  'sub escapestr {
      $_[0] =~ s/([^\x20-\x7E])/sprintf("\\x%02X", ord $1)/egr
   }
   say escapestr($ARGV[0])',
   "\x80"])
80

##</code><code>##

package New;
use v5.36;
use Path::UTiny; # imagine a unicode-aware Path::Tiny

# Create directory named "\xC4\x80"
path("\x{100}")->mkdir;

for (path(".")->children) {
  # compares as unicode
  Old->foo($_) if $_->name eq /\x{100}/;
}

package Old;
use v5.36;

sub foo($dir) {
  # stringify to bytes, creates file "\xC4\x80/\x80.txt"
  open my $f, '>', "$dir/\x80.txt";
}

##</code><code>##

$path= path("$path/$unicode")