Arvados

nested-array.cwl

cwlVersion: cwl:draft-3
class: CommandLineTool
baseCommand: echo
inputs:
  - id: letters
    type:
      type: array
      items:
        type: array
        items: string
    inputBinding:
      position: 1
outputs: []

letters: [[a]]

$ cwl-runner nested-array.cwl nested-array-job.yml 
/home/jiayong/miniconda2/bin/cwl-runner 1.0.20160708190014
[job nested-array.cwl] /tmp/tmpOqjIQT$ echo \
    a \
    a
a a
Final process status is success
{}