package Foo;
sub new { bless {}, shift }
sub get { $_[0]->{$_[1]} }
sub set { $_[0]->{$_[1]} = $_[2] }

package main;
my @list = (Foo->new, Foo->new, Foo->new);

$list[0]->set('a', 'b');
$list[1]->set('b', 'a');
$list[2]->set('x', 'y');

my $isa_foo = sub { UNIVERSAL::isa(shift, 'Foo') };

print join ',', map_recursive(\@list, $isa_foo);

##</code><code>##

my @list2 = ( {a => 'm'}, { 1 => 55}, { Foo => 'Bar' });
my $h = sub { UNIVERSAL::isa(shift, 'HASH') };

print join ',', map_recursive (\@list2, $h);