From bf46ea5611ecc94bf9669b316509281ee8d5c39e Mon Sep 17 00:00:00 2001
From: albertony <12441419+albertony@users.noreply.github.com>
Date: Thu, 28 Aug 2025 09:04:37 +0200
Subject: [PATCH] docs: add some more details about supported regex syntax

---
 cmd/convmv/convmv.go      | 9 ++++++++-
 docs/content/filtering.md | 6 +++---
 2 files changed, 11 insertions(+), 4 deletions(-)

diff --git a/cmd/convmv/convmv.go b/cmd/convmv/convmv.go
index 5a857d703..bb140cfa0 100644
--- a/cmd/convmv/convmv.go
+++ b/cmd/convmv/convmv.go
@@ -34,7 +34,14 @@ var commandDefinition = &cobra.Command{
 	Long: strings.ReplaceAll(`convmv supports advanced path name transformations for converting and renaming
 files and directories by applying prefixes, suffixes, and other alterations.
 
-`+transform.Help()+`Multiple transformations can be used in sequence, applied
+`+transform.Help()+`The regex command generally accepts Perl-style regular expressions, the exact
+syntax is defined in the [Go regular expression reference](https://golang.org/pkg/regexp/syntax/).
+The replacement string may contain capturing group variables, referencing
+capturing groups using the syntax ¡$name¡ or ¡${name}¡, where the name can
+refer to a named capturing group or it can simply be the index as a number.
+To insert a literal $, use $$.
+
+Multiple transformations can be used in sequence, applied
 in the order they are specified on the command line.
 
 The ¡--name-transform¡ flag is also available in ¡sync¡, ¡copy¡, and ¡move¡.
diff --git a/docs/content/filtering.md b/docs/content/filtering.md
index 62f9ccce1..319dccf5b 100644
--- a/docs/content/filtering.md
+++ b/docs/content/filtering.md
@@ -149,9 +149,9 @@ uses) to make things easy for users. However this does not provide
 absolute control over the matching, so for advanced users rclone also
 provides a regular expression syntax.
 
-The regular expressions used are as defined in the [Go regular
-expression reference](https://golang.org/pkg/regexp/syntax/). Regular
-expressions should be enclosed in `{{` `}}`. They will match only the
+Rclone generally accepts Perl-style regular expressions, the exact syntax
+is defined in the [Go regular expression reference](https://golang.org/pkg/regexp/syntax/).
+Regular expressions should be enclosed in `{{` `}}`. They will match only the
 last path segment if the glob doesn't start with `/` or the whole path
 name if it does. Note that rclone does not attempt to parse the
 supplied regular expression, meaning that using any regular expression