c:\@Work\Perl\monks>perl -wMstrict -MO=Deparse,-p -le
"use constant DEBUG => 1;
 ;;
 DEBUG and debugIt();
 ;;
 sub debugIt { print 'debugging it'; }
"
BEGIN { $^W = 1; }
BEGIN { $/ = "\n"; $\ = "\n"; }
use constant ('DEBUG', 1);
use strict 'refs';
debugIt();
sub debugIt {
    use strict 'refs';
    print('debugging it');
}
-e syntax OK

c:\@Work\Perl\monks>perl -wMstrict -MO=Deparse,-p -le
"use constant DEBUG => 0;
 ;;
 DEBUG and debugIt();
 ;;
 sub debugIt { print 'debugging it'; }
"
BEGIN { $^W = 1; }
BEGIN { $/ = "\n"; $\ = "\n"; }
use constant ('DEBUG', 0);
use strict 'refs';
'???';
sub debugIt {
    use strict 'refs';
    print('debugging it');
}
-e syntax OK