I've already realized what this is just symbolic reference

No, it isn't. A symbolic ref uses the string in the variable as the name of a package variable:

my $f = "foo";
our $foo = "blah";
print $$f;

__OUTPUT__
blah
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The behavior you're seeing in your example code is autovivification. You tell Perl that you want a hashref, so you get one. This behavior is forbidden by use strict 'refs'. For that, you should explicitly put a hashref into the variable, such as with my $var = { }; or  my $var = \%hash;.