Dear Brethren, most of us have used code like this: 
use constant DEBUG => 1;
use constant SOMETHINGELSE => 'key';

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This looks fine. However, let's look at this quote from perlsub: 
       Subroutines whose names are in all upper case are reserved to the Perl
       core, as are modules whose names are in all lower case.  A subroutine
       in all capitals is a loosely-held convention meaning it will be called
       indirectly by the run-time system itself, usually due to a triggered
       event.  Subroutines that do special, pre-defined things include
       "AUTOLOAD", "CLONE", "DESTROY" plus all functions mentioned in perltie
       and PerlIO::via.
Now, we all know that constant.pm translates constant names into subroutines... The question is: do we violate Perl conventions by using upper-case constant names? Is that one of those cases where syntactic sugar hurts?

Update: The question has been answered here.

In reply to Constant names come into conflict with Perl style? by dmitri

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