It tells the parser "Hi. Since I have a leading (unary) plus sign, I'm now a scalar expression, so I qualify to match the first item in ok()'s prototype; please do not get confused and interpret me as a class name you should call an ok() method on."

This was done to avoid putting the parens around ok()'s argument, like this:

ok( 
    Mock::Basic->update(
        'mock_basic', 
       { name => 'python' }, 
       {id => 1} 
    ),
    'I should actually put a description on this test'
);
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To me this is a lot clearer; it's less mental effort to just add the parens than it is to dork around trying to remember the parsing rules. Once the parens are there, we've unambiguously declared "these are arguments to a subtroutine called ok(). Please to not attempt to interpret it otherwise, thank you." I'll igonore the fact that there's no description on the test - I think that's more objectionable than the syntax trickery, frankly.

Perhaps you should file a bug on that - feel free to snag this rewrite as a start on a patch.