The tee created by open STDOUT, '|-', tee => $outfile will capture the output of children too, but it won't work well with a custom SIGINT handler.

The tee created by IO::Tee will work with a custom SIGINT handler, but it won't capture the output of executed children.

It sounds like you want to capture the output of children and use a custom SIGINT. Based on my testing, the following does that:

open(STDOUT, '|-',
    bash => (
        -c => 'trap "" INT ; tee -- "$0"',
        $outfile,
    )
) or die;
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Update: Since this is a common problem, tee actually provides a fix for it in the form of -i:

open(STDOUT, '|-',
    tee => ( '-i', '--', $outfile )
) or die;
[download]