I use RE2 and currently achieve this with regular string concatenation. Do you know if they provide an API for doing this without concatenation, and if it would be faster?
The header file is available at https://code.google.com/p/re2/source/browse/re2/set.h , and if I recall correctly, it merges all the regexes into one DFA so that it's faster than just concatenating all your patterns into one string.
