I'm not sure why you interpret what I wrote:

instead of open $file{$key}{fh}, ..., use:

$file{$key}{fh} = cacheout $file{$key}{name}
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as that you should write:

open $file{$key}{fh}, ">", cacheout $file{$key}{name} or die
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Maybe you want to reread my node again. I'm also not sure how to phrase it differently so you get what I mean short of writing the program for you which I won't do.