Regular Expression Engines - PCRE, Boost Regex, Apache Regexp

PCRE - Perl Compatible Regular Expressions

The PCRE library is a set of functions that implement regular expression pattern matching using the same syntax and semantics as Perl 5. PCRE has its own native API, as well as a set of wrapper functions that correspond to the POSIX regular expression API. The PCRE library is free, even for building commercial software.

C++ Regular Expression Engines - PCRE, BOOST REGEX
JAVA Regular Expression Engines - Apache Regexp

Links:

PCRE - http://www.pcre.org/

BOOST Regex - http://www.boost.org/doc/libs/1_35_0/libs/regex/doc/html/index.html

Regular Expressions in C++ with Boost.Regex - http://www.onlamp.com/pub/a/onlamp/2006/04/06/boostregex.html

Apache Regexp - http://projects.apache.org/projects/regexp.html

Regular Expressions in C++ - http://www.ddj.com/184404797

Regular Expression Engines - http://en.wikipedia.org/wiki/Comparison_of_regular_expression_engines