Ask HN: Script/AI/site to parse block of text to sentences?

I periodically download automatic transcriptions off the captioning of YouTube videos. They come in as one large block of lowercase, unpunctuated text. Is there any scripting rules, AI, or other tricks that can parse these into sentences?<p>Example: https:&#x2F;&#x2F;www.youtube.com&#x2F;watch?v=WPPPFqsECz0