Re: Autovivification with hash of hashes

[Aristotle]

Yes you did do something with it. In order to check whether exists $foo{bar}{baz}, obviously, $foo{bar} must be a hash reference. Perl DWIMs (most of the time) by creating an empty hashref on multilevel lookup attempts, but sometimes, like in your case, that is undesired. What you have to do is clunky: check every level of the hierarchy yourself. Something like

my $cursor = \%foo;
for(qw(foo bar)) {
    undef $cursor, last unless exists $cursor->{$_};
    $cursor = $cursor->{$_};
}

print "exists\n" if $cursor;

You want to put this in a function like

sub exists_novivify {
    my $cursor = shift;
    for(@_) {
        undef $cursor, last
            unless exists $cursor->{$_};
        $cursor = $cursor->{$_};
    }
    $cursor;
}

print "exists\n" if exists_novivify \%foo, qw(bar baz);

Update: removed duplicate exists. Thanks BrowserUk.

Makeshifts last the longest.

[Mr_Person]

Thanks! That sorta makes sense, although it's still annoying. I guess that's the price you pay for Perl's flexibility.