How do I modify the shadow password file on a Unix system?

If perl was installed correctly, the getpw*() functions described in the perlfunc manpage provide (read-only) access to the shadow password file. To change the file, make a new shadow password file (the format varies from system to system - see passwd(5) for specifics) and use pwd_mkdb to install it (see pwd_mkdb(5) for more details).