using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Text.RegularExpressions;
 
public class Test
{
	public static void Main()
	{
		var arrayOfWordsToSplitOn = new List<string> { "cat", "dog" };
    	var s = "My cat and my dog are very lazy";
    	var pattern = string.Format(@"\s*\b({0})\b\s*", string.Join("|", arrayOfWordsToSplitOn));
    	var results = Regex.Split(s, pattern).Where(x => !String.IsNullOrWhiteSpace(x)).ToList();
        foreach (var res in results)
        	Console.WriteLine(res);
	}
}

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