The value on the left is the actual name of the form field. This is called URL-encoding, and it happens with data submitted through either GET or POST methods. Your Perl script can convert this information back, but it's often easier to use the POST method when sending long or complex data. GET is mainly useful for short, one-field queries, especially for things like database searches. Private information should always be sent with the POST method, which we'll cover in the next chapter.
GETs are most useful because they can be embedded in a link without needing a form element.
This is often used in conjunction with databases, or instances where you want a single CGI to handle a clearly defined set of options. You could write a single article.cgi to serve up the article, and the CGI would simply look at the query string to figure out which article to display. See Chapter 9 for more on SSIs. This is a variation on the remote host ID script - only here, we show the last page you visited. This script does some pattern-checking to see what browser the visitor is using, and displays a different message depending on browser type.