Accessing DEBUG constant from sub-package

Anonymous Monk has asked for the wisdom of the Perl Monks concerning the following question:

In my main script I set up the debug constant like so:

my $debug;
BEGIN { GetOptions('debug|d' => \$debug) or die }
use constant DEBUG => $ENV{DEBUG} || $debug;
[download]

Then I instantiate a object from a different package:

use Thing;
my $obj = Thing->new;
[download]

I want the $obj to know when it should be in debug mode (the debug value won't change during the script run), but don't want to pass it in as a variable, because then the compiler can't optimize away the debug code. The only way I see to do this is to do this in the Thing package:

use constant DEBUG => &main::DEBUG;
[download]

This doesn't seem very clean. Is there a better way to deal with this, or is it a case of having your optimization and eating it too?

Comment on Accessing DEBUG constant from sub-package Select or Download Code

Replies are listed 'Best First'.
Re: Accessing DEBUG constant from sub-package by BrowserUk (Patriarch) on Aug 09, 2013 at 23:49 UTC
Define the debug code in your modules in terms of `::DEBUG`. Ie: `package Some::Thing; ... if( ::DEBUG ) { ## do debug stuff }` [download] And in main: `use constant DEBUG => 1; ## set to 0 to disable debug and have debug g +uarded code optimised away use Some::Thing; ...` [download] With the rise and rise of 'Social' network sites: 'Computers are making people easier to use everyday' Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error. "Science is about questioning the status quo. Questioning authority". In the absence of evidence, opinion is indistinguishable from prejudice.	[reply] [d/l] [select]
Re: Accessing DEBUG constant from sub-package by tobyink (Canon) on Aug 10, 2013 at 07:06 UTC
Personally I'd do something like this in the Thing package: `use constant DEBUG => main->can("DEBUG") && main->DEBUG;` [download] This makes your Thing package more re-usable, allowing it to be used in scripts that don't define a DEBUG constant in the main package. `package Cow { use Moo; has name => (is => 'lazy', default => sub { 'Mooington' }) } say Cow->new->name`	[reply] [d/l]


Perl Monk, Perl Meditation
	PerlMonks