sub foo { 
    log_msg("In subroutine foo") if $DEBUG
}

##</code><code>##

package Foo;

use strict;
use warnings;

use Attribute::Handlers;

sub _log : ATTR(CODE) {
    my ($package, $symbol) = @_;

    {
        no strict 'refs';
        no warnings 'redefine';
        my $name = *{ $symbol }{NAME};
        my $code = \&{ $package . '::' . $name };

        *{ $package . '::' . $name } = sub {
            my $self = shift;
            print "Entering sub $name\n";
            $code->( $self, @_ );
         };
    }
}


sub foo : _log {
        my $self = shift;

        print "in foo\n";
}

1;

##</code><code>##

Entering sub foo
in foo

##</code><code>##

sub rm_secret_stuff : _authz(admin) { 
   ...
}