It looks as though your telnet daemon on the remote host has been Kerborised (sp?) - so you can log in with an external realm account (either from a Windows domain or MIT Kerberos realm) or with local accounts on the box itself.

It's likely that there's some misconfiguration on the telnetd side or the Kerberos side, either way it's not really a problem with your Perl per-se.

Check your /etc/krb5.conf file on the remote host for a starting point :)