sectokia only showed us the fail case. I assume that his code worked as he expected in the pass case. I should have demonstrated that my code produced the same result in that case.

use strict;
use warnings;
use Data::Dumper;
use Test::More tests=>2;
my $h = { b => { c => { d => 'value' } } };
my $g = $h->{b}{c}{d} if exists($h->{b}{c}) and exists($h->{b}{c}{d});
my $f = $h->{b}{c}{d}//undef;   # Original Code
is( $g, $f, $f );
is_deeply( $h, { b => { c => { d => 'value' } } }, 'no change' );
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The difference between your various f's is not merely one of style, but one of requirements (which we really do not know).