function Get-AllCaps
{
    param(
        [char[]]$InputObject
    )

    If($InputObject.count -eq 1)
    {
        Write-Output $InputObject[0].ToString().ToUpper()
        Write-Output $InputObject[0].ToString().ToLower()
    }
    else
    {
        $cases = Get-AllCaps $InputObject[1..$InputObject.Count]

        foreach($char in ( Get-AllCaps $InputObject[0] ) )
        {
            foreach($line in $cases)
            {
                Write-Output ($char + $line)
            }
        }
    }
}

Get-AllCaps exe