use warnings;
use strict;

package Library::Foo; {
    my $log;
    sub new {
        my ($class, $logger) = @_;
        my $self = bless {}, $class;

        # set the class level log

        $log = $logger->child('Library::Foo');

        # generate a local log per each sub

        my $log = $log->child('new');
        $log->_0("creating new foo obj");

        return $self;
    }
}
package Library; {
    use Logging::Simple;

    # set the class log

    my $log = Logging::Simple->new(name => 'Library');

    sub new {
        my $self = bless {}, shift;

        # generate a child log per sub

        my $log = $log->child('new');
        $log->_0('creating Library obj');

        return $self;
    }
    sub log {
        # return the class level log obj
        return $log;
    }
    sub foo {
        my ($self) = @_;
        my $log = $log->child('foo');
        $log->_0('about to crate lib::foo obj');
        $self->{foo} = Library::Foo->new($self->log);
    }
}

package main;

my $lib = Library->new;

$lib->foo;