Anyways, here it is. Nothing fancy here:

∇R←PEEIGHT;S S←'73167176531330624919225119674426574742355349194934' S←S,'96983520312774506326239578318016984801869478851843' S←S,'85861560789112949495459501737958331952853208805511' S←S,'12540698747158523863050715693290963295227443043557' S←S,'66896648950445244523161731856403098711121722383113' S←S,'62229893423380308135336276614282806444486645238749' S←S,'30358907296290491560440772390713810515859307960866' S←S,'70172427121883998797908792274921901699720888093776' S←S,'65727333001053367881220235421809751254540594752243' S←S,'52584907711670556013604839586446706324415722155397' S←S,'53697817977846174064955149290862569321978468622482' S←S,'83972241375657056057490261407972968652414535100474' S←S,'82166370484403199890008895243450658541227588666881' S←S,'16427171479924442928230863465674813919123162824586' S←S,'17866458359124566529476545682848912883142607690042' S←S,'24219022671055626321111109370544217506941658960408' S←S,'07198403850962455444362981230987879927244284909188' S←S,'84580156166097919133875499200524063689912560717606' S←S,'05886116467109405077541002256983155200055935729725' S←S,'71636269561882670428252483600823257530420752963450'⍝ Find the greatest product of five consecutive digits in S

R←⌈/5×/⎕FI ((2×⍴S)⍴1 0)S

∇