There are several ways to do this, and which ones are best depends a bit on what you're trying to do - normally, a "debug" flag is a global thing, enabled only once by a command line option or environment variable. I'm not sure why you need multiple packages to access it - will the flag be switched on and off during the run of your program? If so, a different design is probably better, because otherwise you may run into issues with the dynamic scope of the setting. To implement only what you've asked so far, I'd suggest to just have a single variable and access it in the Debug package via $Debug::.

use warnings;
use strict;
{
    package Debug;
    use Exporter 'import';
    our @EXPORT = qw/debug/;
    our $FLAG = 0;     # package variable
    sub debug {
        if ($FLAG) {
            print @_;
        }
    }
}
{
    package Foo;
    Debug->import;     # normally "use Debug;"
    $Debug::FLAG = 1;  # global enable
    debug("Hello\n");  # prints "Hello"
}
{
    package Bar;
    Debug->import;      # normally "use Debug;"
    $Debug::FLAG = 0;   # global disable
    debug("World!\n");  # doesn't print
}

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In reply to Re: Overriding Global Variables by haukex
in thread Overriding Global Variables by Mano_Man

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