Finding duplicated files recursively

I was cleaning up a folder with files duplicated in subdirectories. Here is a simple Powershell code that identifies duplications recursively.

There might be a shorter form, but I think this is as I short I can get without becoming very cryptic.

function FindDuplicates
{
  #Receives a list of ArrayLists
  # iteratively prints the full path of each ArrayList item
  # where the ArrayList contains multiple paths (i.e duplicates)
  Process
  {if ($_.Count -gt 1)
    {foreach($d in $_){$d.FullName}}
  }
}

function GetFilesInBuckets($dir,$filter = "*.*")
{
   # Creates a hashtable of arraylists (1 entry per unique file name)
   # Returns the list of arraylists only (not the entire hashtable)
   $files = @{}
   foreach ($fl in (gci $dir -filter $filter -r))
  {
        if(!$files.ContainsKey($fl.Name))
         {$files[$fl.Name] = New-Object System.Collections.ArrayList}
        [void]$files[$fl.Name].Add($fl)
  }
  $files.Values
}

GetFilesInBuckets "C:\MyRootFolder" -f "*.txt"|FindDuplicates

Additional filtering methods will look similar to as "FindDuplicates", and can be piped at the end of the last line of code:

GetFilesInBuckets "C:\MyRootFolder" -f "*.txt"|FindDuplicates|FilterOutOlder