$/ = undef;

Can you explain why you are doing this? I don't see the need and it might complicate matters. I also don't immediately see the need for the look-arounds in the regex. Perhaps if you could provide an SSCCE with a small example of the failing data (a couple of lines should suffice) we might be able to suggest something.

In reply to Re^3: Counting instances of a string in certain sections of files within a hash by hippo
in thread Counting instances of a string in certain sections of files within a hash by Maire

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