How to import term sets to Managed Metadata Service using PowerShell and CSV file

This is the PS script I'm using:

    Param([string]$CentralAdminURL, [string]$TermsCSV, [string]$ADGroup)

    cls
    # loading the term store
    $site = Get-SPSite -Identity($CentralAdminURL)
    $session = new-object Microsoft.SharePoint.Taxonomy.TaxonomySession($site)
    $termstore = $session.TermStores[0]

    # Create a Taxonomy Group
    # I first create a Term Group
    $termGroup = "MY MM Group"
    $group = $termstore.CreateGroup($termGroup)
    $termstore.AddTermStoreAdministrator($ADGroup)
    $group.AddGroupManager($ADGroup)
    $termstore.CommitAll()
    # Import Taxonomy "Know How"
    # Create an instance of ImportManager
    $Importer = $termstore.GetImportManager()
    $varImported = ""
    $varMessages = ""
    $TermSetReader = [System.IO.File]::OpenText($TermsCSV)

    # Syntax: ImportTermSet(TermGroup, TextReader, out isImported, out errorMessage)
    $termset = $Importer.ImportTermSet($group ,$TermSetReader, ([REF] $varImported), ([REF] $varMessages))
    $termset.set_Owner($ADGroup)
    $termset.TermStore.CommitAll()
    Write-Host $varMessages
    Write-Host $varImported
    $site.Dispose()

adapted from the original at http://stevenderveaux.wordpress.com/2010/04/09/import-taxonomy-csv-file-via-powershell/