// define a new exception
class MyException : Exception
{
    ...
}

// throw an exception
Foo() : void
{
    throw MyException();
}

// catching exceptions
try {
    Foo();
}
catch { // catch block uses pattern matching syntax
    |e is MyException => ... // handle exception
    |_ => throw e // rethrow unhandled exception
}
finally {
    ... // code executes whether or not exception was thrown
}