use Getopt::Long;
#Print useage info
sub useage {
    print "\nNifty usage info should go here\n";
    exit;
}
my ($pass, $user, $config_file);


GetOptions(
    'pass=s' => \$pass,
    'user=s' => \$user,
    'config=s' => \$config_file
);

if(defined $config ) {
    # do something
}elsif( defined $user and defined $pass){
# do something}
}else{
    useage();
}