repl.rb

def accept_and_run_command
  loop do
    print "enter command> "
    input = gets.chomp.split(/\s+/)
    
    case input.first
    when "foo" then puts "got command 'foo'"
    when "bar" then puts "got command 'bar'"
    else
      puts "Sorry, but I don't know how to '#{ input.first }'!"
      redo # <-- the redo keyword goes back to the start of the enclosing loop/iterator
    end
  end
end