[ruby]Output nested list with erb

erb_sample.rb

require 'erb'

MY_CATEGORIES = <<SPEC
Fun
<%= ERB.new(FUN, nil, '-').result(binding) -%>
Work
<%= ERB.new(WORK, nil, '-').result(binding) -%>
SPEC

FUN = <<SPEC
  Sport
<%= ERB.new(SPORT, nil, '-').result(binding) -%>
  Friends
SPEC

SPORT = <<SPEC
    Surfing
    Extreme knitting
SPEC

WORK = <<SPEC
  Reports
<%= ERB.new(REPORT, nil, '-').result(binding) -%>
  Trips
SPEC

REPORT = <<SPEC
    Annual
    Status
SPEC

puts ERB.new(MY_CATEGORIES, nil, '-').result(binding)

# Fun
#   Sport
#     Surfing
#     Extreme knitting
#   Friends
# Work
#   Reports
#     Annual
#     Status
#   Trips