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);
}