--eval ≡ evaluate the text
f ≡ formatting function for printing nested values
s ≡ partition a line of text and remove the partition character
⎕FIO ≡ read stdin as byte stream (see FILE_IO.apl)
⎕UCS ≡ convert bytes to characters
⍎ ≡ execute an expression (convert characters to numbers)
SUMMARY:
read stdin as a bytestream
partition at newlines and commas
convert to characters
interpret characters as numbers
disclose into a rank-2 array
format to stdout
slightly verbose example but heres gnu apl as a pipe-like interface. Often this would be abstracted to a library that gets included when you call it:
DESCRIPTION: SUMMARY: