如何在不使用adduser / useradd的情况下管理linux中的用户

I have to create a perl script that allows me to add/delete/modify users from my Debian. I've read that is not recommended but I've been asked to do it without using system calls, so no adduser/useradd allowed. This script should check if a user has been added/deleted from a mysql database and then add the user to the system. Maybe by modifying etc/passwd directly? Is there any perl module to do this?I have to create a perl script that allows me t