in reply to Seeking a way to access a network user's ID
You don't mention what kind of network user log into. You want to search for 'single sign on'. I suspect your users will be authenticating with Active Directory when singing into a Windows domain. For the most part just consider this to be LDAP. Nginx - Configure Active Directory Integration, Mojolicious - authenticating with LDAP(YouTubes link), Net::LDAP.
In Section Seekers of Perl Wisdom