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I don't think I've ever drunk champagne before breakfast before. With breakfast on several occasions, but never before, before.
— Paul Varjak · Breakfast at Tiffany's

Behind the line May contain spoilers.
Our reading
An editorial interpretation.
The speaker distinguishes drinking champagne with breakfast from drinking it before breakfast. Repeating 'before' makes that small difference into a verbal tangle. The joke gives an unusual distinction careful attention, treating a slight change in timing as a noteworthy new experience.
Context reviewed