I fetched the ZIP-file from download, copied all Fonts/*.otf to /usr/share/fonts/truetype and then ran

use strict;
use warnings;

use Tk;

my $f = "STIXGeneral";
my $l = "\x{2014}\x{2014}o\x{2014}\x{2014}";
my $m = MainWindow->new (-title => "STIXtest (P. Assouad)");
   $m->geometry ("400x400+40+40");
my $t = $m->Scrolled ("Text")->pack;
   $t->configure (-font => "{$f} 18 normal");
   $t->insert ("1.0", join "\n" =>
        "$f (Perl-Tk)",
        $l,
        "A B C D  \x{300}x \x{302}x \x{303}x \x{304}x",
        "\x{210C} \x{210E} \x{2112} \x{2115} \x{2202}".
            "\x{2207} \x{2211} \x{221A}",
        $l);
MainLoop ();
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and then got this, which looks pretty OK to me. Note that I left out the braces around normal

This is perl, v5.10.1 (*) built for x86_64-linux
...perl5/site_perl/5.10.1/x86_64-linux/Tk.pm: 804.029
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