perl attribute demo .......................

test2.pl

use strict;
use warnings;
use Data::Dumper::Concise;
use Scalar::Util qw/reftype/;

use constant DEBUG => 1;

use Attribute::Handlers;

sub _log : ATTR(CODE) {
    my ( $pkg, $sym, $code ) = @_;
    print reftype( $_[1] );
    if (DEBUG) {
        my $name = *{$sym}{NAME};
        no warnings 'redefine';
        *{$sym} = sub {
            log_message("Entering sub $pkg\:\:$name");
            my @ret = $code->(@_);
            log_message("Leaving sub $pkg\:\:$name");
            return @ret;
        };
    }
}

sub log_message {
    print shift;
}

sub do_something : _log {
    print "I'm doing something.\n";
}

do_something;