All the message parts you expect are being sent (check the "source text" of the mails in your mail client and you'll see the attachments), but your mail client isn't showing them because MIME::Lite::TT::HTML sets the Content-Type to "multipart/alternative". Set it to "multipart/mixed" manually and you should see the attachments.

...
my $msg = MIME::Lite::TT::HTML->new( 
            From        =>  'ex@why.com',
            To          =>  $params{'emailto'}, 
            Subject     =>  'Your recent purchase', 
            Template    =>  {
                                html    =>  'test.html.tt',
                            },
            TmplOptions =>  \%options, 
            TmplParams  =>  \%params, 
 ); 
$msg->attr("content-type" => "multipart/mixed");
...
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