due to political reasons, the location of routine is fixed!

Sadly, you have two problems: broken code and a broken development process. I wonder to what degree explaining that the development process leads to broken code will help you fix the broken development process.

I wonder to what degree explaining that the development process leads to broken code will help you fix the broken development process.

I know that was a rhetorical question (even without the rhetorical question mark), but I have to comment.

If "political reasons" have already been invoked, it's unlikely that logic will come back into play. This reminds me of a definition of Bigotry: emotional attachment to prejudice (or maybe it was the other way around?). Not sure what the replacement words would be, but "emotional attachment" seems apt.

-QM
--
Quantum Mechanics: The dreams stuff is made of

Could you get away with the following?

{
    my $shared_data;
    my $inner_sub;

    sub outer_sub {
        ...
        ... $inner_sub->(...) ...
        ...
    }

    $inner_sub = sub { ... $shared_data ... };
}
[download]

That would get rid of the bug. (A named sub inside another sub in Perl is a bug in my eyes. The warning is too gentle.)

Note that having any $shared_data makes the function non-reentrant, but you can eliminate that problem by sharing data via parameters.

Update: no warnings 'closure'; with a comment explaining that all shared variables need to be exchanged by parameters or globals would also do the trick. But you're eliminating a very useful check.