Let me tell you from experience - looking at /etc/passwd is badness. There are so many ways that someone may not be using /etc/password (NIS/NIS+, PAM, LDAP, ...) that ... well, just don't. By using the getpw* functions, you tap into the same C runtime library that the OS uses to validate logins. Which means you'll get the value as used on the system, and not some random value.

It's just a good habit to get into. And, besides, File::stat and User::pwent are way too easy to use relative to grepping and spliting the /etc/passwd file. :-)