I'm no expert on filehandles, but I believe it's possible to create a scalar reference to a filehandle (something like this):

my $handle;
open $handle, "filename";
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Then you can create an array of filehandle references and use your $loop variable to index that array. So, instead of FROM_CHILD_$loop, you'd use:

$from_child[ $loop ]
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Cheers,
--Moodster