As per the following URLs re2 is much faster than TRE (on the benchmarks they ran): http://lh3lh3.users.sourceforge.net/reb.shtml http://sljit.sourceforge.net/regex_perf.html re2 is in C++ & has a PCRE API, while TRE is in C & has a POSIX API. Both have BSD copyright. Is it worth considering making re2 posix compliant?