How to compose regex for http requests?

Question

Regular Expressions

There is a script that proxies http requests and can display the result by expression: proxy.exe -l :3333 -r 1.1.1.1:80 -match="Host: (.*)" displays Host: 1.1.1.1 for example Host: 1.0.0.1 was the whole http request displayed?
Like this:

HEAD / HTTP/1.1
Host: 1.0.0.1