After some source diving into the (Perl) source of the pure Perl implementation of Data::Dumper, and some confusion, because usually Perl uses the XS version of Data::Dumper, which behaves differently in this case, I found the following approach works. It monkey-patches Data::Dumper (instead of inheriting from it, because Data::Dumper isn't written that way):

#!perl
use strict;
use warnings;
use utf8;
use charnames ':full'; # just so I can use ASCII to represent Greek le
+tters
use Data::Dumper;

$Data::Dumper::Useperl = 1;
$Data::Dumper::Useqq='utf8';

sub Data::Dumper::qquote {
  local($_) = shift;
  s/([\\\"\@\$])/\\$1/g;

  return qq("$_") unless /[[:^print:]]/;  # fast exit if only printabl
+es

  # Here, there is at least one non-printable to output.  First, trans
+late the
  # escapes.
  s/([\a\b\t\n\f\r\e])/$Data::Dumper::esc{$1}/g;

  # no need for 3 digits in escape for octals not followed by a digit.
  s/($Data::Dumper::low_controls)(?!\d)/'\\'.sprintf('%o',ord($1))/eg;

  # But otherwise use 3 digits
  s/($Data::Dumper::low_controls)/'\\'.sprintf('%03o',ord($1))/eg;

    # all but last branch below not supported --BEHAVIOR SUBJECT TO CH
+ANGE--
  my $high = shift || "";
    if ($high eq "iso8859") {   # Doesn't escape the Latin1 printables
      if ($Data::Dumper::IS_ASCII) {
        s/([\200-\240])/'\\'.sprintf('%o',ord($1))/eg;
      }
      elsif ($] ge 5.007_003) {
        my $high_control = utf8::unicode_to_native(0x9F);
        s/$high_control/sprintf('\\%o',ord($1))/eg;
      }
    } elsif ($high eq "utf8") {
#     Some discussion of what to do here is in
#       https://rt.perl.org/Ticket/Display.html?id=113088
#     use utf8;
#     $str =~ s/([^\040-\176])/sprintf "\\x{%04x}", ord($1)/ge;
    } elsif ($high eq "8bit") {
        # leave it as it is
    } else {
      s/([[:^ascii:]])/'\\'.sprintf('%03o',ord($1))/eg;
      #s/([^\040-\176])/sprintf "\\x{%04x}", ord($1)/ge;
    }

  return qq("$_");
};

my $pv = {
    "\N{GREEK SMALL LETTER ALPHA}\N{GREEK SMALL LETTER BETA}" => "\N{G
+REEK CAPITAL LETTER GAMMA}\N{GREEK CAPITAL LETTER DELTA}"
};

print Dumper $pv;

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In reply to Re: Convert JSON to Perl and back with unicode by Corion
in thread Convert JSON to Perl and back with unicode by bliako

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