Perl Debugged

5.1. Dumping Your Data

That is all well and good for scalars and arrays, but it won't even handle hashes, let alone complex lists of lists. A good way to deal with those is to use the Dumper function in the Data::Dumper module which will let you print out, nicely formatted, anything you give it, no matter how complex:

use Data::Dumper;
# set %state from some database or flat file
warn Dumper(\%state);

which produces

$VAR1 = {
          'WI' => {
                    'BIRD'         => 'Robin',
                    'NAME'         => 'Wisconsin',
                    'LARGEST_CITY' => 'Milwaukee',
                    'CAPITAL'      => 'Madison',
                    'FLOWER'       => 'Wood Violet'
                  },
          'MS' => {
                    'BIRD'         => 'Mockingbird',
                    'NAME'         => 'Mississippi',
                    'LARGEST_CITY' => 'Jackson',
                    'CAPITAL'      => 'Jackson',
                    'FLOWER'       => 'Magnolia'
                  },
[...]

Note that we passed a reference to the ...