Can you reduce your problem to a complete module that is reduced to a short self-contained example that reproduces the problem?

Note that it is really weird to declare your subroutines with a prototype indicating no parameters and then to call the subroutines with actual parameters.

If you are really, really intent on moving to the new (but still experimental) function parameters as in your second example, you will have to modify all your source code to the second style. With Filter::signatures, you can then use the new style in almost all versions of Perl. You have to tell Perl that you want to use experimental features:

use feature 'signatures;

sub example( $foo, $bar='baz' ) {
    ...
}
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But personally, I would recommend against making such a sweeping change right during the move between Perl versions.

Your simplified third style is what I would expect you to start out with, but as your code is in the first style, changing to the third style is inconvenient at this time too.

For me, your first example compiles without problems, so can you show us a stand-alone version that fails perl -wc so we can reproduce your situation?