sub _log : ATTR(CODE) {
    my ($pkg, $sym, $code) = @_;
    if ( DEBUG ) {
        my $name = *{ $sym }{NAME};

        no warnings 'redefine'; # Turn off symbol redefinitions within the block.

        *{ $sym } = sub {
            log_message ($logfile{$pkg}, "Entering sub $pkg\:\:$name\n");
            my @ret = $code->( @_ );
            log_message ($logfile{$pkg}, "Leaving sub $pkg\:\:$name\n");
            return @ret;
        };
    }
}