How to add users to the Visitor group of a Sharepoint 2010 application using Powershell

There has been a need in my company to add the users to the default visitor group of the sharepoint 2010 application. It is really very time consuming when you have to do it one by one using the Sharepoint UI. I have written a small script for which you can add the users to the default visitor group without any issues.
Here, in the below Script, users.txt contain the list of users that need to be added to the Visitors group...
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$Users = Get-Content "C:\Users\service\Documents\PowerShell\users.txt"
foreach ($User in $Users)
{
$url = "http://server1"
$SPUser = New-SPUser -UserAlias $User -Web $url
$Group = "test"
$Owner = "service\account"
$SPSite = Get-SPSite $url
$SPWeb = Get-SPWeb $url
$OpenWeb = $SPSite.OpenWeb()
$OpenWeb.Update()
## can use the below two lines to add a single user to the Visitor Group
#$OpenWeb.SiteGroups.Web.AssociatedVisitorGroup.AddUser
#($Owner,"ps@ms.com",$Group,$Group)
$OpenWeb.SiteGroups.Web.AssociatedVisitorGroup.AddUser($SPUser)
$OpenWeb.Update()
$OpenWeb.Dispose()
}
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Hope this helps some one...