Function Get-Decision ( $Decision ) {
    Switch ( $Decision.toupper() ) {
        "Y" { $Decision = $True }
        "N" { $Decision = $False }
        Default { "Enter a ''Y'' for Yes or a ''N'' for No." ;
            $Decision = $null
            Get-Decision $( Read-Host $Question ) }
    }
    Return ( $Decision )
}
 
$Question = "Remove files?"
Get-Decision $( Read-Host $Question )