# Your host override hash
my %hosts = (
   'foo.bar.com'=>'1.2.3.4',
   'bar.baz.com'=>'4.3.2.1',
);

. . . . .  .

# Get your server name from whereever
my $server = XXXXXXX;

# Override the server name if you have an override
$server = $hosts{$server} if exists $hosts{$server};

# and pass it along to the function/service you're using...
my $result = function_wanting_host($server);