In neither of your examples are you using a reference. Try something more like:

use strict;
use warnings;

my %hash = (foo => 1, bar => 2,);

# pass reference to subroutine
test(\%hash);

########## SUB #########
sub test{
    my $reference = shift; # reference is passed in @_
    print "REF: $reference\n";
    print "KEY: " . $_ . " VAL: " . $reference->{$_} . "\n" for (keys 
+%$reference);
}
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Check out perlref and References quick reference for more info on references and dereferencing! HTH!