Powershell closing Excel objects with ReleaseComObject leaves dangling posh variables

Per this link:

http://social.technet.microsoft.com/Forums/en-US/ITCG/thread/81dcbbd7-f6cc-47ec-8537-db23e5ae5e2f

the correct way to avoid Excel zombies is to release all ComObjects in the powershell environment / script by invoking:

while ([System.Runtime.InteropServices.Marshal]::ReleaseComObject($comobject)) {}
}

on each posh variable holding a reference to a COM object, and to do so in "reverse" order (suitably defined).

"Correct" means specifically"leaves no invisible lurking Excel apps behind".

The recipe works for me when I invoke my scripts as (say):

$ ./script.ps1

But when I invoke the script as:

. ./script.ps1

and then list posh variables:

$ ls variable:

posh throws an error when it encounters the first variable that (previously) held a ComObject reference:

ls : COM object that has been separated from its underlying RCW cannot be used.
At line:1 char:1+ ls variable:+ ~~~~~~~~~~~~~~~~~~+ CategoryInfo          : NotSpecified: (:) [Get-ChildItem], InvalidComObjectException+ FullyQualifiedErrorId : System.Runtime.InteropServices.InvalidComObjectException,Microsoft.PowerShell.Commands.GetChildItemCommand

I tried rv'ing the posh variables, but when I do so prior to the ReleaseComObject, I no longer have a handle to the Com Object; alternatively when I rv the posh variable after ReleaseComObject, posh throws the same error as above.

How to release both the Com Object and the posh variable in the base posh environment (ie . ./script) while avoiding Excel zombies?

Code excerpts below:

function release($foo) {
	while ([System.Runtime.InteropServices.Marshal]::ReleaseComObject($foo)) {}
}

function killExcel()
{
	$xl.displayalerts = $false
	for ($i=1; $i -lt $wss.count; $i++) {
		$wss.Item(1).Delete()
	}
	release $wss
	$wb.close($false, $false, $false)
	release $wb
}

function quit()
{
	killExcel
	$xl.Quit()
	release $xl
	[gc]::collect()
	[gc]::WaitForPendingFinalizers()
	exit
}
...
// read xml file, define xmltitle variable
...
// define $count = # workbook pages

...

$xl = new-object -comobject Excel.Application
$xl.Visible = $True

$xl.DefaultFilePath = (Get-Location).ToString() + "SpreadSheets.d\"
$xl.DefaultFilePath.ToString()
%{$title = $xmltitle.split()}
$title[1] = $title[1] -replace "[.]","dot"

$filename=$xl.DefaultFilePath.ToString() + $title[1] + "_" + $title[2] + ".xlsx"
$filename.ToString()

$xl.sheetsInNewWorkbook = $count
$wb = $xl.Workbooks.Add()
$wss = $wb.worksheets
$sstoc = $wss.Item(1)
$sstoc.name = "Table of Contents"
$sscells = $sstoc.cells
$sscells.item(1,1) = $xmltoc.index

release $sscells
release $sstoc

try {
	$wb.saveas($filename, $xlFileFormat::xlWorkbookDefault)
}
catch [system.exception] {
     // ignore it
}

quit

TIA for the help.

FWIW, I'm running Win7 and Office 2010 in a Workstation 8 VM.

Jim Snyder