script 1

foreach (qw/a b c d/){$hash{$_}++};
print keys %hash, "\n";
print keys %{$hash{'wrong'}};
print keys %hash, "\n";

OUTPUT:

cabd
cwrongabd

---------------------------------
script 2 

foreach (qw/a b c d/){$hash{$_}++};
print keys %hash, "\n";
print $hash{'wrong'};
print keys %hash, "\n";

OUTPUT:

cabd
cabd