use strict;
use UNIVERSAL 'isa';

sub deep_grep (&@) {
  my $test = shift;
  
  my ( @results, %seen );
  
  while ( scalar @_ ) {
    my $target = shift @_;
    
    push @results, grep $test->( $_ ), $target; 
    
    unshift @_, $seen{$target} ++        ? ()              : 
                  isa($target, 'HASH')   ? values %$target :
                  isa($target, 'ARRAY')  ? @$target        :
                  isa($target, 'REF')    ? $$target        :
                  isa($target, 'SCALAR') ? $$target        : ();
  }
  return @results;
}

##</code><code>##

my @loggers = deep_grep( sub { isa( $_, 'Log' ) }, $target );

my @loggers = deep_grep { isa( $_, 'Log' ) } $target;