i.e. I expect $h{x} to hold a hash

That's the clue - you expect that, but it isn't. You look at the box, and you are dereferencing that undef value explicitly as a hash. If you access keys/values of an undef value, your dereference happens implicitly and the hashref is created (autovivification): 

use strict;
my $f;
$f->{foo} = 'bar'; # okay
my ($h, %new);
%new = %$h;        # not okay

[download]

Said otherwise, if you dereference something, you state that it is a reference, which is different to autovivication of an undef value into something.

Clearer?

--shmem 

_($_=" "x(1<<5)."?\n".q·/)Oo.  G°\        /
                              /\_¯/(q    /
----------------------------  \__(m.====·.(_("always off the crowd"))."·
");sub _{s./.($e="'Itrs `mnsgdq Gdbj O`qkdq")=~y/"-y/#-z/;$e.e && print}

In reply to Re^5: Keys() required to autovivify? by shmem
in thread Keys() required to autovivify? by jrw

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