Sounds like a usecase for Enum.chunk_while or the Stream.chunk_while counterpart.

That’s… not a thing.

The strict definition of a CSV would be a file that conforms to RFC4180 - comma delimited, fields with commas escaped with " etc

The “loose” definition expands that to using single characters other than , (tabs, pipes, etc) as a delimiter.

But saying “the delimiter is =>” stretches that definition beyond reason.

Regarding your original question, +1 for starting with Stream.chunk_while. A possible sequence of operations could look like this:

• use Stream.chunk_while to bring together each line starting with a letter and all the following lines that start with a number
• Stream.flat_map over each of those chunks:
  • one row of output with number: nil for the line that starts with the letter
  • one row of output for each line that starts with a number using the letter from above

To answer your specific question: no, you cannot assign a value to a variable in a higher scope

So even if it was a good idea, you couldn’t do it.