run.rb

$:.unshift './lib'
require 'slop'

opts = Slop.new do |o|
  o.string :n, :name, 'Your name'
  o.int :age, 'How old you is'
  o.bool :verbose, 'Enable verbose mode', default: false
end

opts.parse

module Slop::Types
  class ArrayType < Slop::Type
    aliases :list

    def initialize
      @items = []
    end

    def call(value)
      @items.concat value.split(delimiter, limit)
    end

    private

    def delimiter
      options[:delimiter] || ","
    end

    def limit
      options[:limit] || 0
    end
  end
end

opts = Slop.parse %w(--people jon:james) do |o|
  o.array :people, delimiter: ':'
end

opts[:people] #=> ['jon', 'james']