cowsay is a command line program written in Perl. The original version had a final release in 2016 (that’s the version of many installed cowsay programs) and there’s a number of forks of that release in Perl. There are also many many versions of cowsay in other programming languages, like the one I maintain written in R, unimaginatively called cowsay. I wrote about cowsay here back in 2014.