pdl> $x = zeroes 3,2,2; $y = $x-> clump( 1,2 )
pdl> p $y

[
 [0 0 0]
 [0 0 0]
 [0 0 0]
 [0 0 0]
]

pdl> $x .= 3
pdl> p $x, $y, $y-> uniqvec

[
 [
  [3 3 3]
  [3 3 3]
 ]
 [
  [3 3 3]
  [3 3 3]
 ]
]

[
 [0 0 0]
 [0 0 0]
 [0 0 0]
 [0 0 0]
]

[
 [0 0 0]
]