in reply to Re^3: saving a file using a temporary file's handle
in thread saving a file using a temporary file's handle

I think the answer to your quandry is given in the warnings section of File::Temp where it says: 

You will have to clear the close-on-exec bit on that file descriptor 
before passing it to another process.

use Fcntl qw/F_SETFD F_GETFD/;
    fcntl($tmpfh, F_SETFD, 0)
        or die "Can't clear close-on-exec flag on temp fh: $!\n";

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