Trying to Uninstall SCOM agents using script below

Hi There,

I have be trying to run a script i found on this site but with no Joy. the script is :

$list = get-content C:\Hostnames.txt
$agents = foreach($agent in $list){get-agent | where{$_.ComputerName -eq $agent}}
Uninstall-Agent -AgentManagedComputer $agents

where i am just trying with a test server in the Hostnames.txt file. when i run this script i get the below error:

Uninstall-Agent : Cannot validate argument on parameter 'AgentManagedComputer'. The
 argument is null or empty. Supply an argument that is not null or empty and then try the command again.
At C:\scom.ps1:3 char:38
+ Uninstall-Agent -AgentManagedComputer <<<<  $agents
    + CategoryInfo          : InvalidData: (:) [Uninstall-Agent], ParameterBinding
   ValidationException
    + FullyQualifiedErrorId : ParameterArgumentValidationError,Microsoft.Enterpris
   eManagement.OperationsManager.ClientShell.UninstallAgentManagedComputerCmdlet                                                       Is there anything i am doing wrong here? or is there another way of uninstalling over a 100 SCOM 2007 R2 agents from servers.  Many Thanks for any feedback.