Reported-by: Niall McGee
Bug: https://twitter.com/niallmcgee/status/
1686523075423322113
Closes #11571
must consist of no other letters than a-z, A-Z, 0-9 or underscore. The
specified content is then associated with this identifier.
-The name must be unique within a command line invoke, setting the same
-variable name again will be ignored.
+Setting the same variable name again will overwrite the old contents with the
+new.
The contents of a variable can be referenced in a later command line option
when that option name is prefixed with "--expand-", and the name is used as