+To access this functionality without the core overrides, pass the
+C<use> an empty import list, and then access function functions
+with their full qualified names. The built-ins are always still
+available via the C<CORE::> pseudo-package.
+
+=head2 System Specifics
+
+Perl believes that no machine ever has more than one of C<change>,
+C<age>, or C<quota> implemented, nor more than one of either
+C<comment> or C<class>. Some machines do not support C<expire>,
+C<gecos>, or allegedly, C<passwd>. You may call these methods
+no matter what machine you're on, but they return C<undef> if
+unimplemented.
+
+You may ask whether one of these was implemented on the system Perl
+was built on by asking the importable C<pw_has> function about them.
+This function returns true if all parameters are supported fields
+on the build platform, false if one or more were not, and raises
+and exception if you asked about a field that Perl never knows how
+to provide. Parameters may be in a space-separated string, or as
+separate arguments. If you pass no parameters, the function returns
+the list of C<struct pwd> fields supported by your build platform's
+C library, as a list in list context, or a space-separated string
+in scalar context. Note that just because your C library had
+a field doesn't necessarily mean that it's fully implemented on
+that system.
+
+Interpretation of the C<gecos> field varies between systems, but
+traditionally holds 4 comma-separated fields containing the user's
+full name, office location, work phone number, and home phone number.
+An C<&> in the gecos field should be replaced by the user's properly
+capitalized login C<name>. The C<shell> field, if blank, must be
+assumed to be F</bin/sh>. Perl does not do this for you. The
+C<passwd> is one-way hashed garble, not clear text, and may not be
+unhashed save by brute-force guessing. Secure systems use more a
+more secure hashing than DES. On systems supporting shadow password
+systems, Perl automatically returns the shadow password entry when
+called by a suitably empowered user, even if your underlying
+vendor-provided C library was too short-sighted to realize it should
+do this.
+
+See passwd(5) and getpwent(3) for details.