#!perl -l
my $s = "foo";        # a scalar
print ref($s);        # prints nothing: $s is a scalar, not a ref
my $sr = \$s;         # a reference to a scalar
print ref($sr);       # prints SCALAR
my %h;                # a hash
print ref(%h);        # prints nothing: %h is a hash, not a ref
my $hr = \%h;         # a reference to a hash
print ref($hr);       # prints HASH
my $hrr = \$hr;       # a reference to a reference to a hash
print ref($hrr);      # prints REF