use strict;
use UNIVERSAL 'isa';

sub build_deep_sub {
  my %options = @_;
  
  my $sub = q/ sub / . ( $options{proto} ? "($options{proto})" : '' ) . q/ {
    / . ( $options{init} ) . q/
    my ( @results, %seen );
    
    while ( scalar @_ ) {
      my $target = shift;
      / . ( $options{guard} ? "next unless grep { $options{guard} } \$target;" : "" ) . q/
      push @results, / . ( $options{map} ) . q/ $target;
      
      / . ( $options{post_order} ? 'push' : 'unshift' ) . q/  @_,
      / . ( $options{guard} ? "  grep { $options{guard} }" : "" ) . q/
	$seen{$target} ++        ? ()       :	
	  isa($target, 'HASH')   ? %$target :
	  isa($target, 'ARRAY')  ? @$target :
	  isa($target, 'REF')    ? $$target :
	  isa($target, 'SCALAR') ? $$target : ();
    }
    @results;
  } /;
  eval $sub or die "$@: $sub";
}

my $type_search = build_deep_sub( init => 'my $type = shift;', map => 'grep isa( $_, $type ), ', guard => 'ref($_)' );

my @loggers = $type_search->( 'Log', $target );