Search recursively for Duplicate Keys

Hello Experts,

Below script successfully derives the results found or not-found to out-file(s), but if the csv file contains more than one key it does not out-file the values to third file as duplicates found.

Experts i am newbie and needs your help to modify the script to search recursively for values in csv file and if found create a out-file and append the duplicates in them. So result will be three text files 1. Value found 2.No Value found 3. Duplicate Value found.

Expecting a favourable reply.

$txtFile = Get-Content -Path "C:\alex\txtToReadFrom.txt" | Select-Object -Skip 1

foreach ($line in $txtFile)
{
$txtFileName = $line.Split('|')[1]
$txtValueToCheck = $line.Split('|')[4]
 
 if (!(Test-Path -Path "C:\alex\$txtFileName.csv"))
 {
  $line | Out-File "C:\alex\txtNoFileOrValueExist.txt" -Append
 
  continue 
 }
 
 $txtContains = Select-String -Path "C:\alex\$txtFileName.csv" -Pattern $txtValueToCheck
 
 if ($txtContains)
 {
        Write-Output "txtContains equals: $txtContains"
        $fieldAppend = $txtContains.Line.ToString().Split('|')[0, 2] -join '|'
 
        Add-Content "C:\alex\txtForOutput.txt" ($line + $fieldAppend)
 
 }
 else
 {
  $line | Out-File "C:\alex\txtNoFileOrValueExist.txt" -Append
 }
}