Would not it be easier just to code 
use Getopt::Long;
GetOptions("debug" => \$debug_switch);
or even 
use Getopt::Long;
GetOptions("debug+" => \$debug_switch);
which allows several levels of debugging.

In reply to Rex3: (tye) change 'use constant' value through commandline arguments? by Sweeper
in thread change 'use constant' value through commandline arguments? by neuroball

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