sendmail is a common Unix Mail Transport Agent (MTA). It also runs on Windows and other platforms, but that's not the point. The FAQ recommends it because it's pretty likely that any Unix workstation will have it running.

If you don't, take a look at a module like Net::SMTP or something like that. Anything on CPAN with SMTP (Simple Mail Transfer Protocol) will work for you. sendmail configuration is way beyond the scope of Perl programming, and a little tricky in its own right.