package User;
use strict;
...
sub new  {
    my ($pkg,$pw, $userName, $home,$shell) = @_;
         bless {
                 password => $pw || "Changeme", 
                 name    => $userName,
                 home    => $home || "/usr/home/$userName",
                 shell   => $shell || "/usr/bin/bash"
         }, $pkg;
}

sub changePasswd { 
    my $obj = shift; 
    my $oldPassword = shift;
    my $newPassword = shift;
    ...
    $obj->{password} = newPassword; 
}
...
1;