If all you do is "encrypt" the password in a cookie, and let the cookie all that's needed for authentication, using of a cookie is hardly any more secure than sending the password. If an attacker snoops the cookie, he/she can pretent to be the user. About the only protection this cookie scheme offers is towards the user - if she uses the same password for different sites, an attacker can't use the cookie (assuming the attacker doesn't know the decryption key) to log in as the user to a different site.

Off course, discussing these kinds of schemes has hardly anything to do with Perl. The level of protection offered doesn't depend on the language you are creating the cookies in.

Abigail