Actually you have make that object visible. Please find below the code :

#!/usr/bin/perl -w
use Tk;
use Win32::OLE;
use Win32::OLE::Const;
my $mw = MainWindow->new;


$mw->Button(-text => "Run (Closed  Widget)",
            -command => sub { $mw->destroy() })->pack;
$mw->Button(-text => "Run (Opened Widget)",
            -command => sub { oleTest() })->pack;

MainLoop;

oleTest();


sub oleTest
{
    my $word = CreateObject Win32::OLE 'Word.Application' or die $!;
    $word->{'Visible'} = 1;
    my $document = $word->Documents->Add();    
    print "Before OLE\n";
    $document->InlineShapes->AddOLEObject("EMBED",'C:\tmp\test.dat'); 
+# this can be ANY test.dat
    print "After OLE\n";
    $document->SaveAs('c:\tmp\test.docx');    
    $document->activewindow->{'Visible'}="True";
}
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