this script uses 'command_tree' gem to define a tree of commands for the terminal

hydra.rb

#!/usr/bin/env ruby
require 'command_tree'

t = CommandTree::Tree.new

# You register functions here to be executed with characters sequence
t.register('a', 'Greetings')
t.register('ag', 'Greeting') { puts 'hello' }
t.register('aG', 'Greeting special') { puts 'hello man.' } # character are case sensitive
t.register('as', 'Sup') { puts 'Sup man' }

t.register('g', 'Goodbyes')
t.register('gg', 'Salam') { puts "Salam man" }
t.register('gu', 'See you') { puts "See you tomorrow" }

t.show