You could also use the reftype function from Scalar::Util. This has the advantage of

1. Explicitly returning undef on a non-reference variable
2. Returning the underlying data structure type when handed an object

for example:

use Scalar::Util qw(reftype);

my $o=bless {},MyClass;

print ref $o       # prints "MyClass"
print reftype($o)  # prints "HASH"
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