A work around may be to use Data::Dump::Streamer instead:

#!/usr/bin/perl -w

use Encode;
use utf8;

use Data::Dump::Streamer;
#$Data::Dumper::Useperl = 1;

my $string =  'ä, ö, ü / Ä, Ö, Ü, ß ¿Adónde vas?';

$string = encode_utf8( $string ) ;


my $print_count = 1;
my $hash = { key => $string };
my $tmp = Dump ($hash)->Out ();
print "1:$tmp\n";


# Turning $Data::Dumper::Userperl to 0 causes a segfault in the second
+ dumper;
$hash = eval $tmp;
print "Value is : $hash->{key}\n";
$tmp = Dump ($hash)->Out ();
print "2:$tmp\n";

$hash = eval $tmp;
print "Value is : $hash->{key}\n";
$tmp = Dump ($hash)->Out();
print "2:$tmp\n";
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Prints:

Subroutine B::SV::object_2svref redefined at C:/Perl/lib/DynaLoader.pm
+ line 253.
1:$HASH1 = { key => "\344, \366, \374 / \304, \326, \334, \337 \277Ad\
+363nde vas?" };

Value is : ä, ö, ü / Ä, Ö, Ü, ß ¿Adónde vas?
2:$HASH1 = { key => "\344, \366, \374 / \304, \326, \334, \337 \277Ad\
+363nde vas?" };

Value is : ä, ö, ü / Ä, Ö, Ü, ß ¿Adónde vas?
2:$HASH1 = { key => "\344, \366, \374 / \304, \326, \334, \337 \277Ad\
+363nde vas?" };
[download]