To send a cookie from a CGI program, simply send the Set-cookie header sometime before the end of your headers, like this:

$crlf = "\x0d\x0a";        
$cookiehead = "UserID=007";  

print "content-type: text/html$crlf";
print "set-cookie: $cookiehead$crlf";
print "$crlf";
...rest of program

To see what cookies are coming back from the client, check the $ENV{HTTP_COOKIE} variable like this:

$cookie = $ENV{HTTP_COOKIE};
print "<p>Here's a cookie: $cookie<br>\n" if $cookie;

It is valuable to keep in mind (especially when you are testing your code!) that you won't see the cookie come back from the browser until the next connection. It takes a whole round-trip (in other words, Connection A: send the cookie to the browser; Connection B: get the cookie from the browser) for the cookie to appear.

Click the quiz link below for another exciting and challenging (and brief) multiple choice quiz on cookies.
Set Perl Cookie - Quiz