But careful with mixed data structures and the risk of accidental symbolic references. strict can catch that.

An example: 

my %hash;
$hash{beta} = 'x';
for my $name ( qw(alpha beta) ) {
    push @{$hash{$name}}, 123, 456;
}

use Data::Dumper;
print Dumper \%hash;

[download]
Result: 
$VAR1 = {
          'alpha' => [
                       123,
                       456
                     ],
          'beta' => 'x'
        };

[download]
So... where's the array data for 'beta'? It's in the global variable @x. Witness: append this line to the above script: 
print Dumper \@x;

[download]
Result: 
$VAR1 = [
          123,
          456
        ];

[download]

With strict enabled, it'll get caught while trying to push the data: insert the line 

use strict;

[download]
at the top of the script and comment out the line, dumping @x, we appended earlier: 
Can't use string ("x") as an ARRAY ref while "strict refs" in use at t
+est.pl line 6.

[download]

Nasty if you didn't expect it.

The risk of running into it is greatest when using data structures of unequal depth.

In reply to Re^2: How to declare a hash of array? by bart
in thread How to declare a hash of array? by richyau

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