I don't know if this is helpful or not?
I ran:

use strict;
use warnings;

open my $fh, '>'. "testingwrite" or die;

my $count = 20;

while ($count--)
{
   print $fh "count = $count\n";
   sleep (5);
}
[download]

in one Win10 command window.

Then I ran ">handle testingwrite" in another command window:

C:\Users\xxx\Documents\PerlProjects>handle testingwrite

Nthandle v4.22 - Handle viewer
Copyright (C) 1997-2019 Mark Russinovich
Sysinternals - www.sysinternals.com

perl.exe   pid: 2488   type: File   E8: C:\Users\xxx\Documents\PerlPro
+jects\testingwrite

C:\Users\xxx\Documents\PerlProjects>
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This will give you the pid of processes that have an open file handle to "testingwrite".

handle is freeware from Microsoft as part of sysinternals.