Simpler, clearer, more self-contained test: 

#!/usr/bin/perl

use warnings;
use strict;

use IPC::Open3;
use Test::More tests => 1;

# Hide undesired output.
open(STDOUT, '>', '/dev/nul');
open(STDERR, '>', '/dev/nul');

# Associate STDOUT and STDERR with
# descriptors other than 1 and 2.
open(local *STDOUT, '>', '/dev/nul');
open(local *STDERR, '>', '/dev/nul');

open3(
   undef,
   local *PIPE,
   undef,
   'echo out ; echo err >&2',
);

my $pipe = '';
$pipe .= $_ while <PIPE>;
is($pipe, "out\nerr\n");

[download]

Still unix-specific, though.

In reply to Re: IPC::Open3 misbehaving when STDOUT is not FD #1 by ikegami
in thread IPC::Open3 misbehaving when STDOUT is not FD #1 by sgifford

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