ArrayList.Add ... whatever ... | Out-Null

Its not implicitly returning. The return value wasn't assigned so it is emitted to the pipeline.

OK, sorry (there is an explicit "return" keyword that I thought worked the same way). Either way, yes, I know you can avoid it by piping to Out-Null, but that behavior is surprising.

    return {expression}

is equivalent to

    {expression}
    return

the only place you have an exit from a function, script block or similar is either at the end or at a return statement. Every value that isn't assigned or piped into nirvana gets pushed to the pipeline. I actually can't remember having used return statements more often than once or twice so far (and I use PowerShell daily, heavily).

Then I rarely found the need to use ArrayList. Sure, you can use it, but you can just as well do

    $array = @()
    $array += $item

A personal pet peeve of mine is actually that lots of people write PowerShell very similar to equivalent VBScript or C# code. And that makes for horrible PowerShell code (in my eyes). The pipeline is immensely powerful and not using it often makes for pretty crappy code.

Most people writing PowerShell scripts are likely dabblers though. Anyway, I have to admit I don't really appreciate the whole pipeline idea; I just know that `$something = Some-Function` sometimes wouldn't do what I thought it would because of these semantics.