If you want to see how Perl sees and parses your code (and in particular, via the  -p "extra parens, please" switch, how it interprets precedence), use the O and Deparse modules:

>perl -wMstrict -MO=Deparse,-p -le
"my ($node, $disk, %vxdgs) = (0, 0);
 my $vxdg;
 (exists $vxdgs{$node}{$disk}) ? $vxdg = $vxdgs{$node}{$disk}
                               : $vxdg = '';
"
BEGIN { $^W = 1; }
BEGIN { $/ = "\n"; $\ = "\n"; }
use strict 'refs';
(my($node, $disk, %vxdgs) = (0, 0));
my($vxdg);
((exists($vxdgs{$node}{$disk}) ? ($vxdg = $vxdgs{$node}{$disk}) : $vxd
+g) = '');
-e syntax OK
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