Powershell executing If Statement when condition is not met - powershell

Question

I am having an issue with my If/Else statement where it will successfully prompt the user until either a "Y/y" or an "N/n" are entered and will store the proper response in the $input variable outside of the Do/Until loop but will execute the first block of code in the following If Statement whether $input is equal to "Y/y" or "N/n"
How can I make it so the If Statement will only execute when $input is equal to "Y/y" and otherwise if it's "N/n" just execute the empty else and move on to the next $program in $InstallList?
I've tried using an ElseIf and checking for "N/n" but it still only executes the first If Statement.
I've also put Write-Host for $input as a check after it leaves the Do/Until loop and it is the correct input but all falls apart when it moves on to executing the If/Else Statement.
Please help.
foreach($program in $InstallList){
if($program -notin $Installed){
$input = ""
do {
$input = Read-Host -Prompt "$($Program) is not installed would you like to install now? (y/n)"
}
until(($input -eq "y") -or ($input -eq "n"))
if($input -eq "y")
{
Write-ProgressHelper -Message "Installing $($Program)" -StepNumber ($stepCounter++)
Start-Sleep -Seconds 3
Start-Process $Software.$program -Wait
Write-Host "$($Software) installed`n"
}
else {}
else{}
}

Answer 1

Abraham Zinala correctly states that use of $input as a custom variable should be avoided, because it is an automatic variable whose value is managed by PowerShell itself, namely to reflect pipeline input.
It is unfortunate that PowerShell even lets you assign a value, which is a problem that affects other automatic variables too - see this answer.
Technically, as long as you stay within the same scope, you can get away with using $input for custom purposes - though it should still be avoided.
Since this constraint is fulfilled in your code, use of $input is not the source of your problem; there is no obvious problem with your code.
Here's version of your code that avoids use of $input and streamlines ensuring that the user input is valid via the -in operator:
foreach ($program in $InstallList) {
if ($program -notin $Installed) {
do {
$response = Read-Host -Prompt "$($Program) is not installed would you like to install now? (y/n)"
} until ($response -in 'y', 'n')
if ($response -eq 'y') {
'yes' # ... install
}
}
}