Handle command-line switches in Ruby without if...else block

In a blog post about unconditional programming it recommends writing code that limits if statements.

How do I handle command-line switches without if statements?

For example using OptionParser I made a cat clone that will upcase the stream if the --upcase switch is set:

#!/usr/bin/env ruby

require 'optparse'

options = {}
OptionParser.new do |opts|
  opts.banner = "Concatenate files or read from stdin\nUsage: argf_options_parser [options] [file ...]"

  opts.on("-u", "--upcase", "Upcase stream") do
    options[:upcase] = true
  end
end.parse!

if options[:upcase]
  puts ARGF.read.upcase
else
  puts ARGF.read
end

How would I handle that switch without an if..else block?

Also looking for general strategies for writing unconditional code.