How do I print a hash structure in Perl?

Question

Examples:

%hash = (2010 => 21, 2009=> 9);

$hash = {
    a => {
        0 => {test => 1},
        1 => {test => 2},
        2 => {test => 3},
        3 => {test => 4},
    },
};

How do I print the hash?

Answer 1

Do you want to print the entire hash, or specific key, value pairs? And what is your desired result? IF it's just for debugging purposes, you can do something like:

use Data::Dumper;
print Dumper %hash; # or \%hash to encapsulate it as a single hashref entity;

You can use the each function if you don't care about ordering:

while ( my($key, $value) = each %hash ) {
    print "$key = $value\n";
}

Or the for / foreach construct if you want to sort it:

for my $key ( sort keys %hash ) {
    print "$key = $hash{$key}\n";
}

Or if you want only certain values, you can use a hash slice, e.g.:

print "@hash{qw{2009 2010}}\n";

etc, etc. There is always more than one way to do it, though it helps to know what you're frying to do first :)