So will 
#!/usr/bin/perl
print <<'__EOI__';
PIPE: out 1
PIPE: out 2
PIPE: out 3
PIPE: err 1
PIPE: err 2
PIPE: err 3
__EOI__

[download]

True, but completely unhelpful.

I posted my comments to the OP in RT.

In reply to Re^2: 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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