If I have understood your code correctly you are attempting to open the same file twice within the same code (once for writing and once for reading) to different filehandles. One of the filehandles is a bareword and the other is a scalar (why?). You neither close nor flush the writing filehandle before opening the reading one. It is therefore not surprising that you have problems.

If we remove the MSWin specific stuff, we can show a simple, working example like this.

#!/usr/bin/env perl 
use strict;
use warnings;
use autodie;
use IO::Handle;

open my $fh, '+>', 'foo.txt';
print $fh "foo\nbar\nbaz\n";
$fh->flush;
seek $fh, 0, 0;
while (<$fh>) {
    print "Read: $_";
}
close $fh;
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There's only one filehandle, one open and IO::Handle allows us to flush it on demand.