By default, the findRE function finds all matches. You can limit the number of matches with an optional LIMIT parameter.
When specifying the regular expression, use a raw string literal (backticks) instead of an interpreted string literal (double quotes) to simplify the syntax. With an interpreted string literal you must escape backslashes.
The syntax of the regular expression is the same general syntax used by Perl, Python, and other languages. More precisely, it is the syntax accepted by RE2 except for \C.
This example returns a slice of all second level headings (h2 elements) within the rendered .Content:
The s flag causes . to match \n as well, allowing us to find an h2 element that contains newlines.
To limit the number of matches to one:
In Hugo 0.110.0 we added a variant of findRe that returns a slice of strings holding the text of the leftmost match of the regular expression in s and the matches, if any, of its subexpressions.