Powershell changing type

ChangeVariableTypeFail.ps1

function ChangeType
{
    [CmdletBinding()]
    param (
        [string] $input
    )

    $ErrorActionPreference = "Stop"

    $input = $input.Split(',')
    Write-Output "Type after splitting: $($input.GetType().FullName)"
}

$arrayAsString = "a,b,c,d"
Write-Output "Type prior to splitting: $($arrayAsString.GetType().FullName)"

ChangeType -input $arrayAsString -Verbose

<#
  Result:
  
  Type prior to splitting: System.String
  Type after splitting: System.String
#>

ChangeVariableTypeSuccess.ps1

$arrayAsString = "a,b,c,d"
Write-Output "Type prior to splitting: $($arrayAsString.GetType().FullName)"

$arrayAsString = $arrayAsString.Split(',')
Write-Output "Type after splitting: $($arrayAsString.GetType().FullName)"

<#
  Result:
  
  Type prior to splitting: System.String
  Type after splitting: System.String[]
#>