Try to follow the logic of your program. You are reading the value of the "favourite ice cream" cookie, and storing it in $tasty, but you don't check it anywhere. The first part of the script says 'if there is no value in the "flavor" parameter (stored in $favourite), then print normal headers, and the "please select a flavor" form.' If you call the script with no parameters, this is what it is going to do.

What you need to do is to check the value of the cookie before you check the parameters. ie:

#!/usr/bin/perl

use strict;
use warnings;
use CGI qw(:standard);
use CGI::Carp qw(fatalsToBrowser);

my $cookiename = "favorite ice cream";
my $favorite   = param('flavor');
my $tasty      = cookie($cookiename);
my $pass       = url_param('pass');

# First check if we saved a cookie last time
if($tasty)
{
  print header(),
  start_html("Ice Cookies, #2"),
  h1("Hello Ice Cream");
  print "You have already chosen a favorite!";
  print("You have chose as your favorite flavor '$tasty'.");
  print end_html();
  exit;
}

# No cookie, so if no favourite value, print new form
unless ($favorite eq "test")
{
 print header(), start_html("Ice Cookies"), h1("Hello Ice Cream"),
       hr(), start_form(),
       p("Please select a flavor: ", textfield("flavor",$tasty)),
       end_form(), hr();
 exit;
}

# Favourite value was 'test', save cookie to browser
my $cookie = cookie(
 -NAME    => $cookiename,
 -VALUE   => $favorite,
 -PATH    => "/",
 -EXPIRES => "+2y",
);

print header(-COOKIE => $cookie),
 start_html("Ice Cookies, #2"),
 h1("Hello Ice Cream");
print "You have already chosen a favorite!";
print "<a href=\"example.pl?who=pass\">new window</a>";
 #p("You have chose as your favorite flavor '$favorite'.");

# No idea what this is for..
if ($pass) {
print "Still logged in";
}
[download]

The code gets executed from top to bottom..

C.