正则假设有一个多字符的片断重复出现，把"really"、"really really "，以及任意数量连续出现的"really"字符串换成一个简单的"very ” ( Billy tried really hard Sally tried really really hard Timmy tried really really really hard Johnny tried really really really really hard )

可以使用正则表达式来实现这个替换操作，具体方法如下：

1. 使用正则表达式匹配多个连续的"really"字符串，可以使用正则表达式"\b(really\s+){2,}\b"，其中"\b"表示单词边界，"\s+"表示一个或多个空格。

2. 将匹配到的字符串替换为"very "，可以使用字符串的replace方法，将匹配到的字符串替换为"very "即可。

完整代码如下：

import re

s = "Billy tried really hard Sally tried really really hard Timmy tried really really really hard Johnny tried really really really really hard"

# 使用正则表达式匹配多个连续的"really"字符串
pattern = r'\b(really\s+){2,}\b'
result = re.sub(pattern, 'very ', s)

print(result)

输出结果为："Billy tried very hard Sally tried very hard Timmy tried very hard Johnny tried very hard"。