Short answer, you can't. People can turn off cookies in every major browser now.
in reply to Checking Cookies Support with Perl
If you must do cookies that way, maybe you can mark the ones that are returned and purge the ones that never get used after a short period?
Alternately, you can do a two stage cookie drop where you send them a "cookie request" cookie and then only make a long term cookie if they have that cookie. But then you have to work out a strategy for url "marking" the people who wouldn't accept the cookie and ignoring them.
$you = new YOU;
honk() if $you->love(perl)