using System;
using System.Text.RegularExpressions;
public class Example
{
public static void Main()
{
string pattern = @"(?!^)(?<!\d[.A-Z])(?<!\d[A-Z]\.)\b(?=\d+(?:[a-zA-Z]|\.)\s+\p{Lu})";
string substitution = @"\n-----------\n";
string input = @"5. SCOPE This document outlines what to do in case of emergency landing (ignore for non-emergency landings) on tarmac. 6. WHEELS Never land on tarmac. Unless you have lowered the plane wheel mechanism. 6.1 Lower the wheel mechanism using the 2 Switches labelled 'wheel mechanism'. 7A WARNING 7A.1 Do not forget to warn passengers.
";
Regex regex = new Regex(pattern);
string result = regex.Replace(input, substitution);
}
}
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for C#, please visit: https://msdn.microsoft.com/en-us/library/system.text.regularexpressions.regex(v=vs.110).aspx