Regular expression library like Perl and Ruby's regular expressions. This package has a module RegexPR. And RegexPR export functions matchRegexPR and gsubRegexPR.
gsubRegexPR "\\G(\\d\\d\\d)" "\\1," "123456 789" => "123,456, 789"
subRegexPR "(?<=(.)(.)(.))e" " \\3\\2\\1 " "abcdefg" => "abcd dcb fg"