Merge pull request #9249 from tjanez/doc-add_note_about_escaping_with_regex_replace

Added a note about escaping backreferences when using 'regex_replace' filter

docsite/rst/playbooks_variables.rst

@@ -441,6 +441,9 @@ To replace text in a string with regex, use the "regex_replace" filter::
     # convert "foobar" to "bar"
     {{ 'foobar' | regex_replace('^f.*o(.*)$', '\\1') }}
 
+.. note:: If "regex_replace" filter is used with variables inside YAML arguments (as opposed to simpler 'key=value' arguments),
+   then you need to escape backreferences (e.g. ``\\1``) with 4 backslashes (``\\\\``) instead of 2 (``\\``).
+
 A few useful filters are typically added with each new Ansible release.  The development documentation shows
 how to extend Ansible filters by writing your own as plugins, though in general, we encourage new ones
 to be added to core so everyone can make use of them.