Text::CSV_XS versions before 1.65 for Perl allow quadratic CPU use by copying the unparsed remainder per record of CR-only input in getline. With eol unset, the default, getline reads with Perl's default line separator, so input with CR-only line endings arrives as one chunk. After each record the parser copies the whole unparsed remainder into a new buffer, which the next call parses and copies again, so the work grows with the square of the input size. A reader with default options that is sent CSV with classic Mac line endings spends seconds of CPU time on a megabyte of input.