Question

my $crazy_hash = {

  'One' => 1,

  'Two' => 1,

  'Three' => 1,

};


 foreach my $num (keys %crazy_hash) {
      #DoSomething    
  }

The error I get is:

Global symbol “%crazy_hash” requires explicit package name at blah line blah

If I do my %crazy_hash and define it within the loop, it works. Why doesn’t it work as is?

Answer 1

$crazy_hash is a reference to an anonymous hash. Prior to 5.14, you need to dereference the reference for keys to work:

for my $num (keys %{$crazy_hash}) {

Starting with 5.14:

Starting with Perl 5.14, keys can take a scalar EXPR, which must contain a reference to an unblessed hash or array. The argument will be dereferenced automatically. This aspect of keys is considered highly experimental. The exact behaviour may change in a future version of Perl.