'Hello world!'
Hello world!

Here are some redundant alternatives:
   [data=. 'Hello world!'
Hello world!
   data
Hello world!
   smoutput data
Hello world!

   NB. unassigned names are verbs of infinite rank awaiting definition.
   NB. j pretty prints the train.
   Hello World!
Hello World !


   NB. j is glorious, and you should know this!

   i. 2 3   NB. an array of integers
0 1 2
3 4 5

   verb_with_infinite_rank =: 'Hello world!'"_

   verb_with_infinite_rank i. 2 3
Hello world!
   

   verb_with_atomic_rank =: 'Hello world!'"0

   verb_with_atomic_rank i. 2 3
Hello world!
Hello world!
Hello world!

Hello world!
Hello world!
Hello world!