$SIG {__WARN__} = sub {
        require "Carp.pm";
        Carp::cluck @_;
    }
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This will give you a stack trace of from where the warning occurred.

Abigail

Thank you so much! This led me right to the problem, if rather verbosely.

It turns out that whilst streamlining my code, I made incorrect use of a hash slice that brought in more values--some of which were undef--than I had intended; these had no effect on the display but generated errors.

You can use try/catch block from module Error (look at examles in the module documentation and in the article Object Oriented Exception Handling in Perl).

About strange error messages, try to look at perldelta (Perl 5.6.1)::Improved diagnostics.

      
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SV* sv_bless(SV* sv, HV* stash);

Could you elaborate on your suggestion? From reading the documentation of the Error module, and the article you pointed to, it isn't clear to me at all how the Error module could help in catching warnings from already written code.

From what I understood is that the Error module provides you a frame work to set up your own exception handling mechanism, where you can throw exceptions and catch them. Which is something completely different from what the OP wants to do.

Abigail

Generally, you are right, but, in my mind, this problem was because there were not defined some values in the programm. So, using catch of exeptions can help to know, where undefined data were used and corrected them.

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