You've just noticed autovivification. In this case the @{$table{$country}} assumes that the value of $table{$country} must be an array reference and so perl is helpful and just creates it if it doesn't already exists. It's that wrapping @{} that's doing the missing bit for you.

__SIG__
use B;
printf "You are here %08x\n", unpack "L!", unpack "P4", pack
  "L!", B::svref_2object(sub{})->OUTSIDE;
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