This is preliminary documentation for the J807 release
A regular expression is a string that specifies a pattern that is used to search text. You can perform a search for single or multiple matches, or extract the matched text from the string. You can also merge new text in to replace the matches, or apply a verb to the matched text in a string.
As of J807, J uses the PCRE2 (Perl Compatible Regular Expression) engine. See links below.
The Jqt Find in Files utility, available from the Edit menu or by pressing Ctrl+Shift+F, can search for simple texts, regular expressions, or special patterns such as the assignment of a name.