Dylan Thomas line: This appears to be ellipsis (words omitted and understood from the context), which is very often encountered in English. With the "missing" words filled in, it might go something like: These good men, the last wave having gone by them, they are crying out about how bright their frail deeds might have danced in a green bay, and they rage against the dying of the light. Film line: This is also ellipsis.
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