# define a set
$x = [System.Collections.Generic.HashSet[string]]::new()
'python'.ToCharArray().foreach({[void]$x.add($_)})

$y = [System.Collections.Generic.HashSet[string]]::new()
'powershell'.ToCharArray().foreach({[void$y.add($_)})

$x.ExceptWith($y) # All the elements in x but not in y
# union
$x.UnionWith($y) # Unique elements in x or y or both
# intersection
$x.IntersectWith($y) # Elements in both x and y
$x.SymmetricExceptWith($y) # Elements in x or y but not in both