How can I test that "something" is a hash in Perl?

Question

I am receiving a hash of hashes from another function, and some elements of the hash of hashes can be another hash. How can I test to see if something is a hash?

Answer 1

Depending on what you want you will need to use ref or reftype (which is in Scalar::Util, a core module). If the reference is an object, ref will return the class of the object instead of the underlying reference type, reftype will always return the underlying reference type.

if (ref $var eq ref {}) {    print "$var is a hash\n"; }  use Scalar::Util qw/reftype/;  if (reftype $var eq reftype {}) {     print "$var is a hash\n"; } 

Answer 2

Use ref function:

ref($hash_ref) eq 'HASH' ## $hash_ref is reference to hash ref($array_ref) eq 'ARRAY' ## $array_ref is reference to array  ref( $hash{$key} ) eq 'HASH' ## there is reference to hash in $hash{$key}