In Hack, error handling is typically done using exceptions. Hack provides a built-in exception hierarchy that allows you to throw and catch exceptions to handle errors gracefully. Here's how you can handle errors using exceptions in Hack:

1. Throwing an Exception : To indicate an error or exceptional condition, you can throw an exception using the `throw` keyword. An exception is an object that represents an error or exceptional situation.

throw new Exception("An error occurred.");​

In the above example, a new instance of the `Exception` class is created and thrown. You can pass an error message as a parameter to the exception constructor to provide additional information about the error.

2. Catching an Exception : To handle exceptions and prevent them from causing a program to terminate abruptly, you can use the `try` and `catch` blocks. The `try` block contains the code that may throw an exception, and the `catch` block is used to catch and handle the exception.

try {
  // Code that may throw an exception
} catch (Exception $e) {
  // Exception handling code
}​

In the above example, the code within the `try` block is executed, and if an exception is thrown, it is caught by the `catch` block. The exception object is assigned to the variable `$e`, which can be used to access information about the exception, such as the error message. 3.  Multiple Catch Blocks : You can have multiple `catch` blocks to handle different types of exceptions separately. This allows you to handle different exceptional situations differently.

try {
  // Code that may throw an exception
} catch (ExceptionType1 $e) {
  // Exception handling code for ExceptionType1
} catch (ExceptionType2 $e) {
  // Exception handling code for ExceptionType2
}​

In the above example, if an exception of `ExceptionType1` is thrown, it will be caught by the first `catch` block, and if an exception of `ExceptionType2` is thrown, it will be caught by the second `catch` block.

4.  Finally Block : Additionally, you can include a `finally` block after the `catch` block(s). The code within the `finally` block is executed regardless of whether an exception is thrown or not. It is typically used to perform cleanup tasks or release resources.

try {
  // Code that may throw an exception
} catch (Exception $e) {
  // Exception handling code
} finally {
  // Code to be executed regardless of exceptions
}​

In the above example, the code within the `finally` block will always be executed, regardless of whether an exception is thrown or caught.

By using exceptions and the `try-catch` mechanism, you can handle errors in a controlled manner, catch and handle specific types of exceptions, and ensure that your program gracefully handles exceptional conditions.