my %hash_1 = (a => 1, b => 2);
my %hash_2 = (z => 26, y => 25);

foo(\%hash_1, \%hash_2);

sub foo {
    my ($href_1, $href_2) = @_;

    print "$_: $href_1->{$_}\n" for keys %$href_1;    
    print "$_: $href_2->{$_}\n" for keys %$href_2;
}