package MyFirst; 
use strict; use warnings; use feature 'say';
use Log::Any qw/ $log /;

sub do_this {
    say 'Hello from MyFirst';
    $log->debug('This is a debug message');
}

1;

##</code><code>##

package MySecond; 
use strict; use warnings; use feature 'say';
use Log::Any qw/ $log /;

sub do_that {
    say 'Hello from MySecond';
    $log->warn('This is a warning!');
}

1;

##</code><code>##

use strict; use warnings; use feature 'say';

use lib '.';
use MyFirst;
use MySecond;

use Log::Any::Adapter;
use Log::Any::Adapter::Dispatch;

my $logger = Log::Dispatch->new( outputs => [
    [ 'Screen', min_level => 'warning' ],
    [ 'File',   min_level => 'debug', filename  => 'logfile', newline => 1 ],
]);

Log::Any::Adapter->set(
    { category => qr/^My/ },
    'Dispatch',
    dispatcher => $logger,
);

MyFirst::do_this();
MySecond::do_that();

__END__

##</code><code>##

perl 1203778.pl

Hello from MyFirst
Hello from MySecond
This is a warning!

##</code><code>##

$ cat logfile 

This is a debug message
This is a warning!