How to dereference hash references

Question

UPDATE: Everything I know about referencing/dereferencing came from here: http://www.thegeekstuff.com/2010/06/perl-array-reference-examples/

I\'m working with a library

Answer 1

my $hash_ref = @{$result};

is the same as

my @array = @{$result};
my $hash_ref = @array;

This forces the array to be evaluated in scalar context by the assignment operator, which causes it to evaluate as the number of items in the array, or 1.

Answer 2

• We have a %hash.
• To this, we have a hash reference $hashref = \%hash
• This hashref is inside an array @array = ($hashref)
• We get an array reference: $arrayref = \@array

This is our result: $result = $arrayref. Not let's work backwards:

• @result_array = @$result
• $result_hashref = $result_array[0] or combined: $result_hashref = $result->[0]
• %result_hash = %$result_hashref or combined: %result_hash = %{ $result->[0] } (note that these make a copy)
• To get an element in the result hash, we can do
  • $result_hash{$key}
  • $result_hashref->{$key}
  • $result->[0]{$key}

Note that $scalar = @{ $arrayref } does not work as you expect, because an array (which @{ … } is) returns the length of the array in scalar context. To force list context in an assignment, put the left hand side into parens: (…) = here_is_list_context (where … is a list of zero or more lvalues).

Answer 3

If @$result is an array then your LHS must be a list. Otherwise $hashref will be assigned the array size.

my ($hash_ref) = @{ $result};
print Dump($hash_ref));