Named Capturing Groups and Backreferences| www.regular-expressions.info
PCRE2 (Perl Compatible Regular Expressions v2) is an open source library written in C that allows developers to add regular expression support to their applications. The library is compatible with a great number of C compilers and operating systems.| www.regular-expressions.info
In a regular expression, parentheses can be used to group regex tokens together and for creating backreferences. Backreferences allow you to reuse part of the regex match in the regex, or in the replacement text.| www.regular-expressions.info
EditPad Pro is a convenient text editor which supports regular expressions in its powerful search and replace functionality. You can also create custom syntax coloring or highlighting schemes using regular expressions.| www.regular-expressions.info
Use regular expressions with the grep, regexp and sub functions in the base package of the R Project| www.regular-expressions.info