Google code search

Google code search supports POSIX extended regex syntax.

http://www.google.com.au/codesearch?hl=en

Some advance search examples:

• The lang: operator, which restricts by programming language (e.g., lang:"c++", -lang:java, or lang:^(c|c#|c\+\+)$)
• The license: operator, which restricts by software license (e.g., license:apache, -license:gpl, or license:bsd|mit)
• The package: operator, which restricts by package URL (e.g., package:"www.kernel.org" or package:\.tgz$)
• The file: operator, which restricts by filename (e.g., file:include/linux/$ or -file:\.cc$)