sub connect
{
   if (eval { require Net::LDAPS; } and ! $@)
   {
      $ldap = Net::LDAPS->new($_[0]);
   }
   else
   {
      $ldap = Net::LDAP->new($_[0]);
   }
   return $ldap;
}

sub auth
{
   $ldap = connect($_[2]);
   $ldap->bind($_[0],$_[1]) and return $ldap;
}

($dn,$pass,$host) = @ARGV;
auth($dn,$pass,$host) or die "auth failed\n";
$ldap = connect($host);
$ldap->bind($dn,password=>$pass)
...