# Defining the set of values with duplicates.
$array = 'A', 'B', 'C', 'C', 'B'

# Group objects and check for groupings greater than 1 (duplicates)
$Doublon = ($array | Group-Object | Where-Object -FilterScript {$_.Count -gt 1}).Values

# Check condition if duplicates or not
if ($null -eq $Doublon) { 'No duplicates'} else { $Doublon}

# Define the set of values with no duplicates
array = 'A', 'B', 'C'

# Check condition if duplicates or not
if ($null -eq $Doublon) { 'No duplicates'} else { $Doublon}

# And we can transform this code into a function
function Test-Doublon {
  [CmdletBinding()] param (
    [string[]]
    $value )
  #Group objects and check for groupings greater than 1 (duplicates)
  $Doublon = ($Value | Group-Object | Where-Object -FilterScript {$_.Count -gt 1}).Values

  # Check condition if duplicates or not
  if ($null -eq $Doublon) { 'No duplicates'} else { $Doublon }
}
# Possible syntaxes
Test-doublon -value $array
Test-doublon $array
  # Or as a function allowing pipeline values
function test-doublon {
    [CmdletBinding()] param (
    [array][Parameter(ValueFromPipeline)]
    $Value )

    #Group objects and check for groupings greater than 1 (duplicates)
    $Doublon = ($Value | Group-Object | Where-Object -FilterScript {$_.Count -gt 1}).Values

    # Check condition if duplicates or not
    if ($null -eq $Doublon) { 'No duplicates'} else { $Doublon}
  }

# Possible syntaxes
test-doublon -value $array
test-doublon $array
# Use the unary operator (the comma) to send our array as a single element, otherwise the pipeline will process each array value separately
,$array | test-doublon