最近在学习makefile，想搜索一下 $@是啥意思，结果google由于忽略了特殊字符，结果啥也没找到，
后来在stackoverflow上看到了别人同样的问题
http://stackoverflow.com/questions/4685615/search-engine-for-special-characters
其中这个网站俺试了试还不错
SymbolHound is a search engine that doesn't ignore special characters. This means you can easily search for symbols like &, %, and π. We hope SymbolHound will help programmers find information about their chosen languages and frameworks more easily.
Example searches: === javascript scala => lisp #' ruby $$
这个网站貌似主要索引了stackoverflow几个网站的资料，所以主要给俺们马农用用