Your input string is illegal CSV format. From the CSV RFC:
Fields containing line breaks (CRLF), double quotes, and commas
should be enclosed in double-quotes.
However, as a (hacky) workaround, you could disable the quoting behavior by setting the quote string to some character such as $
that is not expected to be found in your input.
csv {
columns => ["label", "num1", "num2", "num3"]
skip_empty_columns => true
quote_char => "$"
}