Hack to enable FOO=bar syntax in PowerShell

OneShotEnvVar.ps1

$ExecutionContext.InvokeCommand.CommandNotFoundAction =
{
    param([string]$commandName,
          [CommandLookupEventArgs]$eventArgs)

    if ($commandName -match "(.*)=(.*)") {
        $var = $matches[1]
        if ($var.StartsWith("get-")) {
            $var = $var.Substring(4)
        }
        $val = $matches[2]
        $eventArgs.CommandScriptBlock = {
            try {
                $backup = Get-Item env:$var -ea Ignore
                Set-Item env:$var $val
                $rest = $args[1..$($args.Length - 1)]
                & $args[0] @rest
            } finally {
                Set-Item env:$var $backup
            }
        }.GetNewClosure()
    }
}