You should show the full cookies here; you can get them out of any dev panel. It would be an egregious security error to put the user name in the cookie though so I’d be surprised if it’s there in any WP version that is even remotely modern. Passing around authentication from one codebase to another based on nothing but a cookie name or value without confirmation—secure, current, valid session lookup—would also be entirely heinous.

It is possible, but your Perl code will need access to the Wordpress database to look up the session. As another monk mentioned, you cannot depend on the cookie alone and must look up the user's session in the database. Cookies can be faked and trusting a username from a cookie is asking for malicious visitors to abuse your site.

This is on a private server with no risk of data loss. It's a very simple reservations system and I'm trying to use the Wordpress login instead of making people login again. I just need the username, not the password.

How would I look up the session without reading the cookie? Not sure how this would work.

Thanks.

You have to use the cookie as a search key to look up the session information wherever WordPress stores it. You need the cookie, but the cookie is an opaque token rather something you meaningfully read to extract information.

Are you asking how to get the cookie in the first place? Is this system on the same domain, such that the user's browser will send the WordPress cookie?

not WP-specific but wouldn't one usually store a session-id (a long random string) into a cookie and then each page you navigate to asks for the cookies, extracts that session-id, and enquires the (server-side) database about the user's details?