perlfaq7.pod has a very related advice:

=head2 How can I catch accesses to undefined variables/functions/metho
+ds?

The AUTOLOAD method, discussed in L<perlsub/"Autoloading"> and
L<perltoot/"AUTOLOAD: Proxy Methods">, lets you capture calls to
undefined functions and methods.

When it comes to undefined variables that would trigger a warning
under C<-w>, you can use a handler to trap the pseudo-signal
C<__WARN__> like this:

    $SIG{__WARN__} = sub {

    for ( $_[0] ) {        # voici un switch statement 

        /Use of uninitialized value/  && do {
        # promote warning to a fatal
        die $_;
        };

        # other warning cases to catch could go here;

        warn $_;
    }

    };
[download]

Adopt that code, and you will be able to "intercept" your warnings and use a value of "$!" at your will
Also, do not forget to protect your code by

  try {
  }
  if ($@) {
     ...
  }
[download]

Jim