Your problem is in

my @lines = unpack ("W*", <INFILE>);
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and you haven't touched $/, so this will just read one line, until the first "\n".

Do

local $/;
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just before you read the file, for example in a bare block, and oh, don't forget to binmode the filehandle if this has to work on something other than Linux, and it'll work fine. It sets this special variable to undef, in case you were wondering, so now you'll read the whole file.