printf "out 1\\nout 2\\nout 3\\n" >&2 will give you the desired output.

Update: While the answer is true, "true" here means "error". Bash is running printf, not perl, so Bash is running into or and die and returning or: command not found and die: command not found; hence, eveything goes to stderr.

In reply to Re: IPC::Open3 misbehaving when STDOUT is not FD #1 by Khen1950fx
in thread IPC::Open3 misbehaving when STDOUT is not FD #1 by sgifford

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