Issue #27528: Document and test warning messages must match at beginning
diff --git a/Doc/library/warnings.rst b/Doc/library/warnings.rst
index 40a0770..3af76ce 100644
--- a/Doc/library/warnings.rst
+++ b/Doc/library/warnings.rst
@@ -140,14 +140,15 @@
| | warnings, regardless of location |
+---------------+----------------------------------------------+
-* *message* is a string containing a regular expression that the warning message
- must match (the match is compiled to always be case-insensitive).
+* *message* is a string containing a regular expression that the start of
+ the warning message must match. The expression is compiled to always be
+ case-insensitive.
* *category* is a class (a subclass of :exc:`Warning`) of which the warning
category must be a subclass in order to match.
* *module* is a string containing a regular expression that the module name must
- match (the match is compiled to be case-sensitive).
+ match. The expression is compiled to be case-sensitive.
* *lineno* is an integer that the line number where the warning occurred must
match, or ``0`` to match all line numbers.