How do the parameters to ;. (Cut) work?

Question

What does <;._1 mean?

data=:',MARY,PATRICIA,LINDA,BARBARA'

<;._1 data

Answer 1

;. is cut: u ;. x y

_1 (x) means "split by the first character"; which is , in this case

< (u) is the verb to apply to each "split". < is box

data (y) is where you apply the cut.

In other words: "Box each split that is made by cutting data at ,s".