Re: usage of if on nested hash creating empty slot for non existing value

[ikegami]

...->{...}
...->[...]

is really equivalent to

( ... //= {} )->{...}
( ... //= [] )->[...]

when they're found in an lvalue context (such as the argument of a function like defined).

You can disable this behaviour for the arguments of defined and exists by adding

no autovivification;

Ref: autovivification