To expand on this to make it a bit more useful:

$SIG{__WARN__} = \&_warn_mess;

sub _warn_mess
{
  require Carp;
  print STDERR Carp::longmess(@_);
}
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This prints out the stack trace at the point of the warning - which I think is what will help the OP the most. I know I've gotten a lot of use out of that to the point where I've put it in its own module at work and can just use it when I need the help ;-)

Update: Missed the extra underscores on __WARN__ and the print for the longmess - thanks to Hue-Bond for alerting me