Regular Expressions for web.page.regex returning unexpected results

When passing a regex parameter to the web.page.regex item, I am not getting the return value expected. What are the supported characters? When using .*\n for example, it returns Cache-Con for the value below. Square brackets '[]' don't seem to be supported either. This is very frustrating.

HTTP/1.1 200 OK
Cache-Control: private
Content-Type: text/html; charset=utf-8
Server: Microsoft-IIS/7.5
X-AspNetMvc-Version: 3.0
X-AspNet-Version: 4.0.30319
X-Powered-By: ASP.NET
Date: Fri, 18 May 2012 13:43:20 GMT
Connection: close
Content-Length: 1

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