Perms ← ⊜∘⊸≠@ "ABCD CABD ACDB DACB BCDA ACBD ADCB CDAB DABC BCAD CADB CDBA CBAD ABDC ADBC BDCA DCBA BACD BADC BDAC CBDA DBCA DCAB"
/⊂≡(▽˜-⊸/↥⊕⊃⧻⊢⊸⊛)⍉ Perms