Oh OK right I see. Part of my error is the shell, and part is perl.

Lifted this from the open docs.

    open OLDERR,">&",\*STDERR or die "Can't dup STDERR: $!";
    open STDERR,'>>',"foo.out" or die "Can't redirect STDERR: $!";
    eval 'use Cache::File';
    open STDERR, ">&OLDERR" or die "Can't dup OLDERR: $!";
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but I get a

Name "main::OLDERR" used only once: possible typo...
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Is there another way to express the last open, or do I have to do the local "no warnings" thing that I read about a couple times many years ago?