IF I understand your question correctly (the code given is broken) this depends again on the quality of your sources.

You could use B::Deparse (->coderef2text) to dynamically reconstruct the source of a given sub and parse the first line with @_ using a regex.

Here are dragons!!!

... this use of @_ is only a convention and not guaranteed.

But again you might only be interested to have a limited personal solution for your IDE....

... but this is life inspection... wouldn't you need static parsing¹???

Please clarify your question!!!

¹)eg with PPI ?