You are probably better off using CGI.pm instead of rolling your own parsing of arguments.

As for checking the password, are you sure you want to reject passwords containing a non-alphanum? Usually you try to enforce hard to guess passwords, your check is promoting easy to guess passwords. Anyway, to enforce a minimum length of 5, replace the + in your regex with {5,}.

As for the line with grep and ypcat, what makes you think that that is valid Perl? And why do you "have to" use ypcat? Anyway, I suggest that you lookup the syntax of grep - then it should become much clearer.

BTW, was this a homework problem?

Abigail