behavior looks consistent when autoflush is activated.

Otherwise please use a similar code-template for a SSCCE.

use v5.12;
use warnings;
use Data::Dump qw/pp dd/;




sub tst {
    my $vers = shift;

    open STDOUT, ">-";                  # restore STDOUT
    $|=1;


    say STDERR "********* testing $vers\n";

    my $fh;

    open $fh, ">-" if $vers eq "open2";
    $fh = \*STDOUT if $vers eq "copyref";
    open $fh, '>&', STDOUT if $vers eq "redirect";


    $fh->autoflush;

    say "$vers 1";

    close STDOUT;

    say $fh "$vers 2";

    say "$vers 3";
}


tst("redirect");

tst("open2");

tst("copyref");
[download]

-*- mode: compilation; default-directory: "d:/tmp/pm/" -*-
Compilation started at Mon Mar  1 23:21:00

C:/Strawberry/perl/bin\perl.exe -w d:/tmp/pm/redirect_STDOUT.pl 
********* testing redirect

redirect 1
redirect 2
say() on closed filehandle STDOUT at d:/tmp/pm/redirect_STDOUT.pl line
+ 32.
********* testing open2

open2 1
open2 2
say() on closed filehandle STDOUT at d:/tmp/pm/redirect_STDOUT.pl line
+ 32.
********* testing copyref

copyref 1
say() on closed filehandle STDOUT at d:/tmp/pm/redirect_STDOUT.pl line
+ 30.
say() on closed filehandle STDOUT at d:/tmp/pm/redirect_STDOUT.pl line
+ 32.

Compilation finished at Mon Mar  1 23:21:00
[download]