news: add entry for regexp-subst

Signed-off-by: shifter <shifter@axoflow.com>

news/fx-feature-409.md

@@ -0,0 +1,24 @@
+### `regex_subst()`: Function Reworked
+
+The `regex_subst()` function has been updated to enhance functionality:
+
+- **Extended Match Group Support**:
+  Replacement strings can now resolve match group references up to 999 groups.
+
+- **Optional Disabling**:
+  The feature can be disabled using the `nogroups` named argument flag.
+
+- **Leading Zero Support**:
+  Match group references with leading zeros (e.g., `\01`, `\002`) are now correctly interpreted. This prevents ambiguity when parsing group IDs, ensuring that shorter IDs like `\1` are not mistakenly interpreted as part of larger numbers like `\12`.
+
+**Example**:
+
+```python
+result = regex_subst("baz,foo,bar", /(\w+),(\w+),(\w+)/, "\\2 \\03 \\1")
+
+# Force disable this feature
+result = regex_subst("baz,foo,bar", /(\w+),(\w+),(\w+)/, "\\2 \\03 \\1", nogroups=True)
+
+# Handling leading zeros
+result = regex_subst("baz,foo,bar", /(\w+),(\w+),(\w+)/, "\\0010") # returns `baz0`
+```