https://metacpan.org/pod/Log::Log4perl
https://www.perl.com/pub/2002/09/11/log4perl.html/
https://www.perlmonks.org/?node_id=1198853

##</code><code>##

use Log::Log4perl;

sub init()
{
    Log::Log4perl->easy_init( 
        {   level    => $DEBUG,
            file     => ">>test.log",
            category => "FILE"
        },
        {   level    => $DEBUG,
            file     => "STDOUT",
            category => "STDOUT"
        }
    );
}

sub getLogger
{
    my ($category) = @_;
    
    my $logger = Log::Log4perl->get_logger($category);
        
    return $logger;
}

init();

my $stdout_logger = getLogger(STDOUT);
$stdout_logger->info("testing stdout logger");

my $file_logger = getLogger(FILE);
$file_logger->info("testing file logger");

##</code><code>##

Log::Log4perl::Logger::APPENDER_BY_NAME{'STDOUT'}->threshold($TRACE);
Log::Log4perl->appender_by_name('STDOUT')->threshold($TRACE);

##</code><code>##

https://metacpan.org/pod/Log::Log4perl#Advanced-configuration-within-Perl