Thanks, that's a good idea. However I can't use it in my case, as there are too many methods in Log.pm to override - they all use couple of instance variables, which should have new values. Ideally this would work for me:

package Redirector;

my $new_obj;
# Redirect all methods calls of object A to object B.
sub redirect
{
  my $new_obj = shift;
  my @methods = @_ || 'all';
  <instrument the methods so that Redirector::foo is called
  instead of old_obj::foo>
}

sub print
{
  my $real_obj = shift;
  # Conveniently switch the object.
  $new_obj->print(@_);
}
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The issue with the above is keeping track of $new_obj. This needs to be a package variable, and the class itself has to be a singleton - unless a hash with package names as keys. Any ideas ? For now, deepcopying looks the simplest solution to me, as the data to be traversed is small in size. But I think your idea can be generalized to a Redirector CPAN module !