using System;
using System.Collections;
using System.Collections.Generic;
using System.Text.RegularExpressions;
 
public class Test
{
	public static void Main()
	{
		var text = "<p>AI.For example <p>A.I<p>BB.";
		var result = new List<string>();
		var rx = new Regex(@"(?=<p>\s*([A-Z])\1*\.)");
		var idx = 0;
		foreach (Match m in rx.Matches(text)) {
			result.Add(text.Substring(idx, m.Index-idx));
			idx = m.Index;
		}
		if (idx < text.Length - 1) {
			result.Add(text.Substring(idx));
		}
		Console.WriteLine(string.Join("\n", result));
	}
}

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