In Perl, how to remove ^M from a file?

Question

I have a script that is appending new fields to an existing CSV, however ^M characters are appearing at the end of the old lines so the new fields end up on a n

Answer 1

Or a 1-liner:

perl -p -i -e 's/\r\n$/\n/g' file1.txt file2.txt ... filen.txt