I think you are getting it wrong, Given/When are activated by the feature pragma with the keyword switch or with an indication of the first Perl version which supports it.(not a Switch module)

The deprecation also affects Given/When, because of the built-in use of smartmatch. We had a discussion recently, should be easily found.

In the post above I updated a link to a thread showing how to easily emulate Given/When with For/If!

HTH! :)