my %params=(
  host => (TYPE=>"s", REQUIRED=>1, VALUE=>undef,
           VALIDATE=>sub { # Tis could be a subref to an external, if it gets too big
                  my $host=shift;
                  print "\nChecking if $host is alive.. \n";
                 $ping = Net::Ping->new();
                 if ($ping->ping($host)){
                    print "$host is alive\n\n";
                 }else {
                    print "$host is unreachable\n\n";
                    exit;
                 }    
                 $ping->close();
                 },
          ), # End of host
 
  engine =>  (TYPE=>"s", REQUIRED=>1, VALUE=>undef,),
  user   =>   (TYPE=>"s", REQUIRED=>1, VALUE=>undef),
  password =>  (TYPE=>"s", REQUIRED=>1, VALUE=>undef),

);

##</code><code>##

GetOptions(
   map { "$_=$params{$_}{TYPE}" => \$params{$_}{VALUE}  } keys %params
  );

for (keys %params){
  showUsage("Missing required parameter $_") if $params{$_}{REQUIRED} && ! $params{$_}{VALUE};
  $params{$_}{VALIDATE}->($params{$_}{VALUE})  if   $params{$_}{VALIDATE};
}