my $logger = Log::Log4perl->get_logger();

open INPUT, '-|', '/some/program/with/verbose/output';

while( my $line <INPUT> )
{
    foreach my $watch_string ( $schema->resultset('WatchString')->all )
    {
        if( $line =~ $watch_string->match_re() )
        {
            # Do stuff
            my $log_message = join(' ', 'Interesting output '. $watch_string->comment, $line);
            $logger->log( $watch_string->log_level, $log_message);
        }
    }
}