$ Card 1: 41 48 83 86 17 | 83 86  6 31 17  9 48 53
$ Card 2: 13 32 20 16 61 | 61 30 68 82 17 32 24 19
$ Card 3:  1 21 53 59 44 | 69 82 63 72 16 21 14  1
$ Card 4: 41 92 73 84 69 | 59 84 76 51 58  5 54 83
$ Card 5: 87 83 26 28 32 | 88 30 70 12 93 22 82 36
$ Card 6: 31 18 13 56 72 | 74 77 10 23 35 67 36 11
TestInput ←

Parse ← ∩(⊜parse≠@ .⊔)⍘⊟⊏1_3 ⊢regex "((\\d+\\s+)+)\\|((\\s+\\d+)+)"

PartIPre ← ⌊ⁿ:2-1/+♭⊞=Parse
PartIPost ← /+

PartIIPre ← /+♭⊞=Parse
PartIIPost ← (
  ⊃(∘|+1⊚⧻)
  ⊙⊙0
  ∧(
    ⊃(⊙⊢|⋅(↘1)|⋅(+⊢))
    ⬚0+×+1⊚
  )
  ;
)

PartIPost ⊜PartIPre ≠@\n. TestInput
PartIIPost ⊜PartIIPre ≠@\n. TestInput

PartIPost ⊜PartIPre ≠@\n. &fras "day04.in"
PartIIPost ⊜PartIIPre ≠@\n. &fras "day04.in"