Look at what my @flds = split '\|', $line; is doing with the lines whose last two fields are empty, e.g. |3104|1|New Years|Holiday|Clinic|||
Unfortunately, it does not return zero-length strings for trailing empty fields, as it ought to (and, I thought, used to).
Instead, it doesn't return them at all; @flds is shorter by two.
So you get undef when you try to access the fields at those indices.