A couple of possible code hacks to avoid autovivication in:

print "defined\n" if (exists($x->{fred}->{dave}));
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1. Use last to abort the statement (adapted from Re: Shortcut operator for $a->{'b'}=$b if $b;):

{ print "defined\n" if (exists(%{$x->{fred}||last}->{dave})); }
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2. Redirect to an anonymous empty hash ref:

print "defined\n" if (exists(%{$x->{fred}||{}}->{dave});
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