local pulses = 0

function getPulses()
  while true do
    os.pullEvent 'redstone'
    if rs.getInput 'left' then
      pulses = pulses + 1
      repeat
        os.pullEvent 'redstone'
      until not rs.getInput 'left'
      pulses = 0
    end
  end
end

function waitForKeyword()
  while true do
    local input = read()
    if input == 'send' then
      for i=1, pulses do
        rs.setInput('right', true)
        sleep(0.1)
        rs.setInput('right', false)
      end
    end
  end
end

parallel.waitForAny(waitForKeyword, getPulses)