In the same way that a script can contain functions, a function can contain other functions. This is shown in the following example:

function Outer {
    param (
        $Parameter1
    )

    function Inner1 {
    }
    function Inner2 {
    }

    Write-Host 'Hello world'
}

This technique can be used to isolate small repeated sections of code with a function.

Nested functions must appear before they are used, but otherwise can appear anywhere in the body of the function.

The disadvantage of nesting a function in this manner is that it becomes much harder to test as a unit of code. The function only exists in the context of its parent function; it cannot be called from the scope above that. This is an important consideration when developing a function as part of a module.