http://blogs.msdn.com/b/powershell/archive/2009/03/12/reserving-keywords.aspx

CanNoutUseUsingKeywork.ps1

function using
{             
    param($obj, [scriptblock]$sb)             
            
    try {             
        & $sb             
    } finally {             
        if ($obj -is [IDisposable]) {             
            $obj.Dispose()             
        }             
    }             
} 


using ($stream = new-object System.IO.StreamReader $PSHOME\types.ps1xml) {
    foreach ($_ in 1..5) { $stream.ReadLine() }             
}