Examining data structures

There are lots of good modules that make this easy. I recommend Data::Printer.

Example code:

eric@eric:~ $ cat foo.pl 
#!/usr/bin/env perl
use strict;
use warnings;
use DDP;

my $data_structure = {
    scalar  => 42,
    listref => [1, 2, 3],
    hashref => {a => 1, b => 2, c => 3},
    coderef => sub { print "hello\n" },
};

p $data_structure;

On the command line:

eric@eric:~ $ perl foo.pl 
\ {
    coderef   sub { ... },
    hashref   {
        a   1,
        b   2,
        c   3
    },
    listref   [
        [0] 1,
        [1] 2,
        [2] 3
    ],
    scalar    42
}